Electrosurgical systems and methods for removing and modifying tissue

ABSTRACT

The present invention provides systems, apparatus and methods for selectively applying electrical energy to body tissue in order to, ablate, contract, coagulate, or otherwise modify a tissue or organ of a patients. An electrosurgical apparatus includes an electrode support bearing an active electrode in the form of a plasma blade or hook having an active edge and first and second blade sides. The active edge is adapted for severing a target tissue via localized molecular dissociation of tissue components. The first and second blade sides are adapted for engaging against, and coagulating, the severed tissue. s. A method of the present invention comprises positioning an electrosurgical probe adjacent to the target tissue so that a blade- or hook-like active electrode is brought into at least close proximity to the target tissue in the presence of an electrically conductive fluid. A high frequency voltage is applied between the active electrode and a return electrode to effect cool ablation or other modification of the target tissue. During application of the high frequency voltage, the electrosurgical apparatus may be translated, reciprocated, or otherwise manipulated such that the active edge is moved with respect to the tissue. The present invention volumetrically ablates or otherwise modifies the target tissue with minimal or no damage to surrounding, non-target tissue.

CROSS-REFERENCES TO RELATED APPLICATIONS

[0001] The present invention claims priority from U.S. ProvisionalPatent Application No. 60/182,751 filed Feb. 16, 2000, which is acontinuation-in-part of U.S. patent application Ser. No. 09/162,117,filed Sep. 28, 1998, now U.S. Pat. No. 6,117,109 (Attorney Docket D-8),which is a continuation in part of U.S. patent application Ser. No.08/977,845, filed Nov. 25, 1997 (Attorney Docket D-2), which is acontinuation-in-part of application Ser. No. 08/562,332, filed Nov. 22,1995, now U.S. Pat. No. 6,024,733 (Attorney Docket 016238-000710), andU.S. patent application Ser. No. 09/041,934, filed Mar. 13, 1998(Attorney Docket A-1-6), which is a continuation-in-part of U.S. patentapplication Ser. No. 08/485,219 (now U.S. Pat. No. 5,697,281), filed onJun. 7, 1995 (Attorney Docket 16238-000600).

[0002] The present invention is also related to commonly assignedcopending U.S. Provisional Patent Application No. 60/062,996, filed Oct.23, 1997 (Attorney Docket 16238-007300), U.S. patent application Ser.No. 08/990,374, filed Dec. 15, 1997 (Attorney Docket E-3), which is acontinuation-in-part of U.S. patent application Ser. No. 08/485,219,filed on Jun. 7, 1995, now U.S. Pat. No. 5,697,281 (Attorney Docket16238-000600), patent application Ser. Nos. 09/109,219, 09/058,571,08/874,173 and 09/002,315, filed on Jun. 30, 1998, Apr. 10, 1998, Jun.13, 1997, and Jan. 2, 1998, respectively (Attorney Docket Nos. CB-1,CB-2, 16238-005600 and C-9, respectively) and U.S. patent applicationSer. No. 09/054,323, filed on Apr. 2, 1998 (Attorney Docket E-5), U.S.patent application Ser. No. 09/010,382, filed Jan. 21, 1998 (AttorneyDocket A-6), and U.S. patent application Ser. No. 09/032,375, filed Feb.27, 1998 (Attorney Docket CB-3), U.S. patent application Ser. Nos.08/977,845, filed on Nov. 25, 1997 (Attorney Docket No. D-2),08/942,580, filed on Oct. 2, 1997 (Attorney Docket 16238-001300), U.S.application Ser. No. 08/753,227, filed on Nov. 22, 1996 (Docket16238-002200), U.S. application Ser. No. 08/687,792, filed on Jul. 18,1996 (Docket No. 16238-001600), and PCT International Application, U.S.National Phase Serial No. PCT/US94/05168, filed on May 10, 1994, nowU.S. Pat. No. 5,697,909 (Attorney Docket 16238-000440), which was acontinuation-in-part of U.S. patent application Ser. No. 08/059,681,filed on May 10, 1993 (Attorney Docket 16238-000420), which was acontinuation-in-part of U.S. patent application Ser. No. 07/958,977,filed on Oct. 9, 1992 (Attorney Docket 16238-000410) which was acontinuation-in-part of U.S. patent application Ser. No. 07/817,575,filed on Jan. 7, 1992 (Attorney Docket 16238-00040), the completedisclosures of which are incorporated herein by reference for allpurposes. The present invention is also related to commonly assignedU.S. Pat. No. 5,683,366, filed Nov. 22, 1995 (Attorney Docket16238-000700), the complete disclosure of which is incorporated hereinby reference for all purposes.

BACKGROUND OF THE INVENTION

[0003] The present invention generally relates to electrosurgicalsystems and methods for ablating, severing, dissecting, contracting, orotherwise modifying target tissues or organs. The invention relates moreparticularly to electrosurgical apparatus and methods for modifying atissue or organ via molecular dissociation of tissue components, whereinthe apparatus includes an active electrode in the form of a plasma bladeor hook. The present invention further relates to electrosurgicalinstruments and methods for harvesting blood vessels such as theinternal mammary artery, the saphenous vein, or the like, for use incoronary artery bypass graft procedures.

[0004] Conventional electrosurgical instruments and techniques arewidely used in surgical procedures because they generally reduce patientbleeding and trauma associated with cutting operations, as compared withmechanical cutting and the like. Conventional electrosurgical proceduresmay be classified as operating in monopolar or bipolar mode. Monopolartechniques rely on external grounding of the patient, where the surgicaldevice defines only a single electrode pole. Bipolar devices have twoelectrodes for the application of current between their surfaces.Conventional electrosurgical devices and procedures, however, sufferfrom a number of disadvantages. For example, conventionalelectrosurgical cutting devices typically operate by creating a voltagedifference between the active electrode and the target tissue, causingan electrical arc to form across the physical gap between the electrodeand the tissue. At the point of contact of the electric arcs with thetissue, rapid tissue heating occurs due to high current density betweenthe electrode and the tissue. This high current density causes cellularfluids to rapidly vaporize into steam, thereby producing a “cuttingeffect” along the pathway of localized tissue heating. Thus, the tissueis parted along the pathway of evaporated cellular fluid, inducingundesirable collateral tissue damage in regions surrounding the targettissue.

[0005] Further, monopolar electrosurgical devices generally directelectric current along a defined path from the exposed or activeelectrode through the patient's body to the return electrode, the latterexternally attached to a suitable location on the patient. This createsthe potential danger that the electric current will flow throughundefined paths in the patient's body, thereby increasing the risk ofunwanted electrical stimulation to portions of the patient's body. Inaddition, since the defined path through the patient's body has arelatively high electrical impedance, large voltage differences musttypically be applied between the return and active electrodes in orderto generate a current suitable for ablation or cutting of the targettissue. This current, however, may inadvertently flow along body pathshaving less impedance than the defined electrical path, which willsubstantially increase the current flowing through these paths, possiblycausing damage to or destroying surrounding tissue.

[0006] Bipolar electrosurgical devices have an inherent advantage overmonopolar devices because the return current path does not flow throughthe patient. In bipolar electrosurgical devices, both the active andreturn electrode are typically exposed so that both electrodes maycontact tissue, thereby providing a return current path from the activeto the return electrode through the tissue. One drawback with thisconfiguration, however, is that the return electrode may cause tissuedesiccation or destruction at its contact point with the patient'stissue. In addition, the active and return electrodes are typicallypositioned close together to ensure that the return current flowsdirectly from the active to the return electrode. The close proximity ofthese electrodes generates the danger that the current will short acrossthe electrodes, possibly impairing the electrical control system and/ordamaging or destroying surrounding tissue.

[0007] In addition, conventional electrosurgical methods are generallyineffective for ablating certain types of tissue, and in certain typesof environments within the body. For example, loose or elasticconnective tissue, such as the synovial tissue in joints, is extremelydifficult (if not impossible) to remove with conventionalelectrosurgical instruments because the flexible tissue tends to moveaway from the instrument when it is brought against this tissue. Sinceconventional techniques rely mainly on conducting current through thetissue, they are not effective when the instrument cannot be broughtadjacent to, or in contact with, the elastic tissue for a sufficientperiod of time to energize the electrode and conduct current through thetissue.

[0008] A prevalent form of cardiovascular disease is atherosclerosis inwhich the cardiovascular system leading to the heart is damaged orobstructed as a result of occluding material in the blood stream.Vascular complications produced by atherosclerosis, such as stenosis,aneurysm, rupture, or occlusion, increase the likelihood of angina,stroke, and heart attacks. In many cases, the obstruction of the bloodstream leading to the heart can be treated by a coronary artery bypassgraft (CABG) procedure.

[0009] In a conventional CABG procedure, the obstruction is bypassed bya vascular conduit established between an arterial blood source and thecoronary artery to a location beyond the obstruction. The vascularconduit is typically a non-critical artery or vein harvested fromelsewhere in the body. In a procedure known as “free bypass graft”, thesaphenous vein is harvested from the patient's leg and is used as thevascular conduit. One end of the saphenous vein is anastomosed to theaorta and the other end is anastomosed to the diseased coronary arteryat a location past the obstruction. In a procedure known as “in situbypass graft”, an internal mammary artery (IMA) is used as the bypassconduit. In an in situ bypass graft procedure, the surgeon dissects asufficient length of the artery from its connective tissue, thentransects the artery and connects the transected end to the diseasedcoronary past the obstruction, and leaves the other end of the IMAattached to the arterial supply.

[0010] The internal mammary arteries are particularly desirable for useas in situ bypass grafts, as they are conveniently located, havediameters and blood flow volumes that are comparable to those ofcoronary arteries, and have superior patency rates. Use of the left orright IMA as a bypass graft first involves harvesting the IMA from theinside chest wall.

[0011] In conventional CABG procedures, access to the IMA is typicallyobtained either through a sternotomy or a gross thoracotomy. In thesternotomy or gross thoracotomy, the surgeon typically uses a saw orother cutting instrument to cut the sternum longitudinally to allow twoopposing halves of the anterior portion of the rib cage to be spreadapart. The opening into the thoracic cavity is created so that thesurgeon may directly visualize the heart and thoracic cavity. However,such methods suffer from numerous drawbacks. For example, thelongitudinal incision in the sternum often results in bone bleeding,which is difficult to stop. The bone bleeding can produce a high degreeof trauma, a larger risk of complications, an extended hospital stay,and a painful recovery period for the patient. Once the surgeon hasaccessed the thoracic cavity, the conventional method of harvesting theIMA involves the use of scalpels or conventional electrosurgicaldevices. A number of disadvantages inherent in conventionalelectrosurgical devices have been set forth hereinabove.

[0012] Thus, there is a need for an electrosurgical apparatus which canbe used for the precise removal or modification of tissue at a specificlocation, wherein a target tissue or organ can be dissected, transected,incised, contracted, and/or coagulated, with minimal, or no, collateraltissue damage. The instant invention provides such an apparatus andrelated methods, wherein tissue may be ablated or otherwise modified bya first region or element of a blade active electrode, and the modifiedtissue can be further modified by a second region or element of theblade active electrode, and wherein the quantity and quality of thetissue modification can be accurately controlled.

SUMMARY OF THE INVENTION

[0013] The present invention generally provides systems, apparatus, andmethods for selectively applying electrical energy to cut, incise,ablate, or otherwise modify a tissue or organ of a patient. In oneaspect, the electrosurgical systems and methods of the invention areuseful for harvesting and dissecting veins and arteries of a patient,such as the saphenous vein or an IMA for use in a CABG procedure.

[0014] In one aspect, the present invention provides a method ofcreating an incision in a body structure. An electrosurgical probe ispositioned adjacent the target tissue so that one or more activeelectrode(s) are brought into at least partial contact or closeproximity with the target tissue. High frequency voltage is then appliedbetween the active electrode(s) and one or more return electrode(s) andthe active electrode(s) are moved, translated, reciprocated, orotherwise manipulated to cut through a portion of the tissue. In someembodiments, an electrically conductive fluid, e.g., isotonic saline orconductive gel, is delivered or applied to the target site tosubstantially surround the active electrode(s) with the fluid. In otherembodiments, the active electrode(s) are immersed within theelectrically conductive fluid. In both embodiments, the high frequencyvoltage may be selected to locally ablate or sever a target tissue,and/or to effect a controlled depth of hemostasis of severed bloodvessels within the tissue. In another aspect, the electrosurgicalsystems and methods of the invention are useful for harvesting anddissecting veins and arteries of a patient, such as the saphenous veinor the IMA for use in a CABG procedure.

[0015] In one aspect, tissue is cut or otherwise modified by moleculardissociation or disintegration processes. (In contrast, in conventionalelectrosurgery tissue is cut by rapidly heating the tissue untilcellular fluids explode, producing a cutting effect along the pathway oflocalized heating.) The present invention volumetrically removes thetissue along the cutting pathway in a cool ablation process thatminimizes thermal damage to surrounding tissue. In these embodiments,the high frequency voltage applied to the active electrode(s) issufficient to vaporize the electrically conductive fluid (e.g., gel orsaline) between the active electrode(s) and the tissue. Within thevaporized fluid, a plasma is formed and charged particles (e.g.,electrons) cause the molecular breakdown or disintegration of thetissue, perhaps to a depth of several cell layers. This moleculardissociation is accompanied by the volumetric removal of the tissue,e.g., along the incision of the tissue. This process can be preciselycontrolled to effect the volumetric removal of tissue as thin as 10microns to 150 microns with minimal heating of, or damage to,surrounding or underlying tissue structures. A more complete descriptionof this phenomenon is described in commonly assigned U.S. Pat. No.5,683,366, the complete disclosure of which is incorporated herein byreference.

[0016] In a specific embodiment, the present invention provides a methodof accessing a patient's thoracic cavity. The active electrode(s) arepositioned in contact or in close proximity to a surface of the sternum.A high frequency voltage is applied between the active electrode(s) anda return electrode. The active electrodes are moved across the sternumto create an incision. In a specific configuration, the sides of theactive electrode are slidingly engaged with the sternum as the incisionis being made, so as to cause coagulation and hemostasis within thesternum.

[0017] In another exemplary embodiment, the present invention provides amethod for harvesting the IMA from a patient. The electrosurgical probeis positioned adjacent the IMA and high frequency electrical energy isapplied between one or more active electrode(s) and one or more returnelectrode(s). The probe is then moved so that the active electrode(s)volumetrically removes connective tissue adjacent to the IMA so that theIMA is free from connective tissue along a portion of its length. In anexemplary embodiment, the probe is positioned adjacent to the IMA, andadvanced along the length of the IMA while high frequency electricalenergy is applied between the active electrode(s) and a return electrodeto remove or cut the connective tissue or other structures surroundingthe IMA. The residual heat from the electrical energy also providessimultaneous hemostasis of severed blood vessels, which increasesvisualization and improves recovery time for the patient. In addition,the ability to simultaneously cut through tissue on either side of theIMA decreases the length of the procedure, which further improvespatient recovery time. After a suitable length of the IMA has beendissected, it may be transected, and anastomosed to a diseased coronaryartery using known methods. In some embodiments, an electricallyconductive fluid (liquid, gas, or gel) is placed at the target siteadjacent to the IMA so as to provide a current flow path between thereturn electrode and the active electrode.

[0018] Apparatus according to the present invention generally include anelectrosurgical instrument, such as a probe or catheter, having a shaftwith proximal and distal ends, one or more active electrode(s) at thedistal end and one or more connectors coupling the active electrode(s)to a source of high frequency electrical energy. The active electrode(s)are preferably designed for cutting tissue; i.e., they typically have adistal edge or point. In one embodiment, a plurality of activeelectrodes are aligned with each other to form a linear electrode arrayfor cutting a path through the tissue. In another exemplary embodiment,the active electrode(s) include a sharp distal point to facilitate thecutting of the target tissue. In one specific configuration, the activeelectrode is a blade having a sharp distal point and sides. As the sharpdistal point incises the tissue, the sides of the blade slidinglycontact the incised tissue. The electrical current flows through thatportion of the tissue in the vicinity of the active electrode and/or theconductive fluid to the return electrode, such that the target tissue isfirst severed, and then the severed tissue is coagulated.

[0019] The apparatus can further include a fluid delivery element fordelivering electrically conductive fluid to the active electrode(s) andthe target site. The fluid delivery element may be located on the probe,e.g., a fluid lumen or tube, or it may be part of a separate instrument.Alternatively, an electrically conductive gel or spray, such as a salineelectrolyte or other conductive gel, may be applied the target site. Inthis embodiment, the apparatus may not have a fluid delivery element. Inboth embodiments, the electrically conductive fluid preferably providesa current flow path between the active electrode(s) and one or morereturn electrode(s). In an exemplary embodiment, the return electrode islocated on the probe and spaced a sufficient distance from the activeelectrode(s) to substantially avoid or minimize current shortingtherebetween and to shield the return electrode from tissue at thetarget site.

[0020] In a specific configuration, the electrosurgical probe includesan electrically insulating electrode support member having a tissuetreatment surface at the distal end of the probe. One or more activeelectrode(s) are coupled to, or integral with, the electrode supportmember such that the active electrode(s) are spaced from the returnelectrode. In one embodiment, the probe includes a plurality of activeelectrode(s) having distal edges linearly aligned with each other toform a sharp cutting path for cutting tissue. The active electrodes arepreferably electrically isolated from each other, and they extend about0.2 mm to about 10 mm distally from the tissue treatment surface of theelectrode support member. In this embodiment, the probe may furtherinclude one or more lumens for delivering electrically conductive fluidto one or more openings around the tissue treatment surface of theelectrode support member. In an exemplary embodiment, the lumen extendsthrough a fluid tube exterior to the probe shaft that ends proximal tothe return electrode.

[0021] In another aspect of the invention, the electrode support membercomprises a plurality of wafer layers bonded together, e.g., by a glassadhesive or the like. The wafer layers each have conductive stripsplated or printed thereon to form the active electrode(s) and the returnelectrode(s). In one embodiment, the proximal end of the wafer layerswill have a number of holes extending from the conductor strips to anexposed surface of the wafer layers for connection to electricalconductor lead traces in the electrosurgical probe or handpiece. Thewafer layers preferably comprise a ceramic material, such as alumina,and the electrode will preferably comprise a metallic material, such asgold, platinum, tungsten, palladium, silver or the like.

[0022] In another aspect of the invention, there is provided anelectrosurgical probe having a blade-like active electrode affixed to anelectrically insulating electrode support on the distal end of a shaft.In a specific configuration, the active electrode is in the form of aplasma blade comprising a substantially flat metal blade having at leastone active edge and first and second blade sides. In one embodiment, theactive electrode comprises a hook. The hook may include a curvedportion. One or more portions of the hook may have a serrated edge. Thereturn electrode is typically located on the shaft distal end proximalto the electrode support. In use, the active electrode and the returnelectrode are coupled to opposite poles of a high frequency powersupply. The active edge may have a variety of shapes, and is adapted forgenerating high current densities thereon, and for precisely severing orablating tissue or an organ in a highly controlled manner via moleculardissociation of tissue components. The first and second blade sides areadapted for engaging with tissue, such as tissue severed by the activeedge, and for coagulating tissue engaged therewith.

[0023] The probe may be provided in various configurations, for example,according to a particular procedure to be performed. Thus, the electrodesupport may be arranged terminally or laterally on the probe, and theblade active electrode may be arranged terminally or laterally on theelectrode support. The active electrode may be provided in variousforms, such as a metal blade of unitary construction, e.g., a metal discor portion thereof, a crosspiece supported by at least one electrodearm, or a hook. The shaft distal end may have a beveled end, a distalcurve, and/or a laterally compressed region. Each of these features orelements of the probe may facilitate accessing a tissue or organtargeted for treatment or modification by the probe. In addition, thelaterally compressed region may be adapted for accommodating theelectrode support.

[0024] According to one aspect of the invention, there is provided amethod for modifying a tissue using an electrosurgical probe having anactive electrode in the form of a single blade which includes at leastone active edge and first and second blade sides. The method involvespositioning the probe such that the active electrode makes contact with,or is in close proximity to, a target tissue; and applying a highfrequency voltage between the active and return electrodes sufficient toprecisely sever or remove target tissue via molecular dissociation oftissue components adjacent to the active edge. The probe may bemanipulated during the application of the high frequency voltage suchthat the active electrode is moved with respect to the target tissue.According to one aspect of the invention, the configuration of theactive electrode (e.g., a hook shaped electrode) is adapted for severingtissue as the probe distal end is drawn or pulled towards the operatorof the probe. In this manner, the extent to which the tissue is severedcan be precisely controlled. Thereafter, the severed tissue may becoagulated upon engagement of the tissue against the first and secondblade sides of the active electrode.

[0025] In another aspect of the invention, there is provided a method ofharvesting a tissue or organ using an electrosurgical probe having anactive electrode in the form of a single blade, wherein the single bladeelectrode includes an active edge and first and second blade sides. Insituations where the tissue to be harvested is concealed by an overlyingtissue, the tissue to be harvested must first be accessed by incising orremoving the overlying tissue. Removal of the overlying tissue may beperformed in various ways, including: 1) mechanically, e.g. using ascalpel, rongeur, surgical saw or drill, etc. or a combination thereof;2) via conventional electrosurgery, e.g., a Bovie; or 3) using anelectrosurgical probe of the instant invention adapted for severingtissue in a cool ablation process. Once the tissue or organ to beharvested is accessible, the tissue or organ to be harvested may bedissected by juxtaposing the active edge of the active electrode againstthe surrounding connective tissue, and applying a high frequency voltagebetween the active and return electrodes sufficient to cause moleculardissociation of connective tissue components. In this way, theconnective tissue adjacent to the active electrode is ablated at atemperature in the range of 40° C. to 70° C., with no, or minimal,thermal damage to the tissue to be harvested.

[0026] The electrosurgical probe of the invention is also applicable toa broad range of other procedures, including without limitation:cutting, resection, ablation, and/or hemostasis of tissues and organssuch as prostate tissue, scar tissue, myocardial tissue, and tissues ofthe knee, shoulder, hip, and other joints; procedures of the head andneck, such as of the ear, mouth, throat, pharynx, larynx, esophagus,nasal cavity, and sinuses; as well as procedures involving skin tissueremoval and/or collagen shrinkage in the epidermis or dermis. A moredetailed account of various treatments and procedures which may becarried out according to the invention is set forth in enabling detailhereinbelow.

[0027] For a further understanding of the nature and advantages of theinvention, reference should be made to the following description takenin conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0028]FIG. 1 is a perspective view of an electrosurgical systemincorporating a power supply and an electrosurgical probe for tissueablation, resection, incision, contraction, vessel harvesting, andhemostasis, according to the present invention;

[0029]FIG. 2 is a side view of an electrosurgical probe according to thepresent invention;

[0030]FIG. 3 is an end view of the distal portion of the probe of FIG.2;

[0031]FIG. 4 is a cross sectional view of the distal portion of theelectrosurgical probe of FIG. 2;

[0032]FIG. 5 is an exploded view of a proximal portion of theelectrosurgical probe;

[0033]FIG. 6 is an end view of an exemplary electrode support comprisinga multi-layer wafer with plated conductors for electrodes;

[0034]FIGS. 7 and 8 are side views of the electrode support of FIG. 7;

[0035] FIGS. 9A-13A are side views of the individual wafer layers of theelectrode support;

[0036] FIGS. 9B-13B are cross-sectional views of the individual waferlayers;

[0037]FIGS. 14 and 15 illustrate an alternative multi-layer wafer designaccording to the present invention;

[0038]FIG. 16 is a perspective view of an electrosurgical probe havingan elongated, blade-like active electrode;

[0039]FIG. 17A-17C are cross-sectional views of the distal portions ofthree different embodiments of an electrosurgical probe according to thepresent invention;

[0040]FIG. 18 illustrates an electrosurgical probe with a 90° distalbend and a lateral fluid lumen;

[0041]FIG. 19 illustrates an electrosurgical system with a separatefluid delivery instrument according to the present invention;

[0042]FIGS. 20A and 20B are cross-sectional and end views, respectively,of yet another electrosurgical probe incorporating flattened activeelectrodes;

[0043]FIG. 21 is a detailed end view of an electrosurgical probe havingan elongate, linear array of active electrodes suitable for use insurgical cutting;

[0044]FIG. 22 is a detailed view of a single active electrode having aflattened end at its distal tip;

[0045]FIG. 23 is a detailed view of a single active electrode having apointed end at its distal tip;

[0046]FIG. 24 is a perspective view of the distal portion of anotherelectrosurgical probe according to the present invention;

[0047]FIG. 25 illustrates another embodiment of the probe of the presentinvention, specifically designed for creating incisions in external skinsurfaces;

[0048]FIG. 26 is a perspective view of another embodiment of anelectrosurgical probe for use in dermatology procedures;

[0049] FIGS. 27A-27C are exploded, isometric views of the probe of FIG.26;

[0050]FIG. 28 is a cross-sectional view of another alternativeelectrosurgical probe;

[0051]FIG. 29 illustrates another embodiment of the electrosurgicalprobe of the present invention, incorporating additional activeelectrodes;

[0052]FIG. 30 is a perspective view of an electrosurgical probe having ablade electrode;

[0053]FIG. 31A is a perspective view, and FIG. 31B is a lateral view, ofa blade electrode, according to one embodiment of the invention;

[0054]FIGS. 32A, 32B, and 32C are a side view, a plan view, and an endview, respectively, of an electrosurgical probe having a bladeelectrode;

[0055]FIGS. 33A and 33B are a side view and a plan view, respectively,of the distal end of an electrosurgical probe having a terminal bladeelectrode, according to one embodiment of the invention;

[0056] FIGS. 33C-33E each show a side view of the distal end of anelectrosurgical probe having a terminal blade electrode, according tothree different embodiments of the invention;

[0057]FIGS. 34A, 34B, and 34C are a side view, a plan view, and an endview, respectively, of an electrosurgical probe having a terminalelectrode support and a lateral blade electrode, according to anotherembodiment of the invention;

[0058]FIGS. 35A, 35B, and 35C are a side view, a plan view, and an endview, respectively, of an electrosurgical probe having a lateralelectrode support and a lateral blade electrode, according to anotherembodiment of the invention;

[0059]FIGS. 36A and 36B each show a side view of the distal end of anelectrosurgical probe having a blade electrode, according to twodifferent embodiments of the invention;

[0060] FIGS. 37A, and 37B are a side view and an end view, respectively,of an electrosurgical probe having a lumen external to the probe shaft,according to one embodiment of the invention;

[0061] FIGS. 38A, and 38B are a side view and an end view, respectively,of an electrosurgical probe having an outer sheath surrounding the probeshaft, according to another embodiment of the invention;

[0062]FIGS. 39A, 39B, and 39C schematically represent a perspectiveview, a longitudinal sectional view, and an end view, respectively, ofan electrosurgical probe, according to another embodiment of theinvention;

[0063]FIG. 39D shows detail of the distal portion of the probe of FIGS.39A-C;

[0064]FIGS. 40A and 40B schematically represent a longitudinal sectionalview, and an end view, respectively, of an electrosurgical probe,according to another embodiment of the invention;

[0065]FIG. 40C shows detail of the distal portion of the probe of FIGS.40A, 40B;

[0066]FIGS. 41A, 41B, and 41C each show detail of the distal portion ofan electrosurgical probe, according to three different embodiments ofthe invention;

[0067]FIGS. 42A and 42B schematically represent a procedure for incisingand coagulating tissue with an electrosurgical probe having a bladeelectrode, according to one embodiment of the invention;

[0068]FIG. 43A schematically represents a number of steps involved in amethod of treating a patient with an electrosurgical probe having ablade electrode, according to one embodiment of the invention;

[0069]FIG. 43B schematically represents a number of steps involved in amethod of concurrently severing and coagulating tissue, according to oneembodiment of the invention; and

[0070]FIG. 44 schematically represents a number of steps involved in amethod of dissecting a tissue or organ of a patient with anelectrosurgical probe, according to another embodiment of the invention.

DESCRIPTION OF THE SPECIFIC EMBODIMENTS

[0071] The present invention provides systems and methods forselectively applying electrical energy to a target location within or ona patient's body, particularly for cutting, ablating, and/or coagulatinga tissue using a blade-like electrode. The instant invention alsoprovides apparatus and methods for making incisions to access a tissueor organ within a patient's body, to dissect or harvest the tissue ororgan from the patient, and to transect or otherwise modify the tissueor organ. In one aspect, the invention provides apparatus and methodsfor dissecting and harvesting blood vessels from a patient.

[0072] The present invention is useful in procedures where the targettissue or organ is, or can be, flooded or submerged with an electricallyconductive fluid, such as isotonic saline. In addition, tissues whichmay be treated by the system and method of the present invention furtherinclude, but are not limited to, tissues of the heart, chest, knee,shoulder, ankle, hip, elbow, hand or foot; as well as prostate tissue,leiomyomas (fibroids) located within the uterus, gingival tissues andmucosal tissues located in the mouth, tumors, scar tissue, myocardialtissue, collagenous tissue within the eye; together with epidermal anddermal tissues on the surface of the skin. The present invention is alsouseful for resecting tissue within accessible sites of the body that aresuitable for electrode loop resection, such as the resection of prostatetissue, leiomyomas (fibroids) located within the uterus, or other tissueto be removed from the body.

[0073] The present invention is also useful for procedures in the headand neck, such as the ear, mouth, throat, pharynx, larynx, esophagus,nasal cavity, and sinuses. These procedures may be performed through themouth or nose using speculae or gags, or using endoscopic techniques,such as functional endoscopic sinus surgery (FESS). These procedures mayinclude the removal of swollen tissue, chronically-diseased inflamed andhypertrophic mucus linings, polyps and/or neoplasms from the variousanatomical sinuses of the skull, the turbinates and nasal passages, inthe tonsil, adenoid, epi-glottic and supra-glottic regions, and salivaryglands, submucus resection of the nasal septum, excision of diseasedtissue and the like. In other procedures, the present invention may beuseful for cutting, resection, ablation and/or hemostasis of tissue inprocedures for treating snoring and obstructive sleep apnea (e.g., UPPPprocedures), for gross tissue removal, such as tonsillectomies,adenoidectomies, tracheal stenosis and vocal cord polyps and lesions, orfor the resection or ablation of facial tumors or tumors within themouth and pharynx, such as glossectomies, laryngectomies, acousticneuroma procedures and nasal ablation procedures. In addition, thepresent invention is useful for procedures within the ear, such asstapedotomies, tympanostomies, myringotomies, or the like.

[0074] The present invention may also be useful for cosmetic and plasticsurgery procedures in the head and neck. For example, the presentinvention is particularly useful for ablation and sculpting of cartilagetissue, such as the cartilage within the nose that is sculpted duringrhinoplasty procedures. The present invention may also be employed forskin tissue removal and/or collagen shrinkage in the epidermis or dermistissue in the head and neck region, e.g., the removal of pigmentations,vascular lesions scars, tattoos, etc., and for other surgical procedureson the skin, such as tissue rejuvenation, cosmetic eye procedures(blepharoplasties), wrinkle removal, tightening muscles for facelifts orbrowlifts, hair removal and/or transplant procedures, etc.

[0075] The present invention is also useful for harvesting bloodvessels, such as a blood vessel to be used as a graft vessel during theCABG procedure, e.g., the saphenous vein and the internal mammary artery(IMA). One or more embodiments of the invention may be used as follows:i) to access the blood vessel to be harvested, e.g., by opening the legto access the saphenous vein, or opening the chest (either via alongitudinal incision of the sternum during an open-chest procedure, orduring a minimally invasive inter-costal procedure); ii) to dissect theblood vessel to be harvested from the surrounding connective tissuealong at least a portion of its length; and iii) to transect thedissected blood vessel at a first position only in the case of apedicled graft (IMA), or at the first position and at a second positionin the case of a free graft (saphenous vein). In each case i) to iii),as well as for other embodiment of the invention, the procedure involvesremoval of tissue by a cool ablation procedure in which a high frequencyvoltage is applied to an active electrode in the vicinity of a targettissue, typically in the presence of an electrically conductive fluid.The cool ablation procedure of the invention is described fullyelsewhere herein. The electrically conductive fluid may be a bodilyfluid such as blood or synovial fluid, intracellular fluid of the targettissue, or isotonic saline delivered to the target tissue during theprocedure. The present invention is also useful for coagulating blood orblood vessels, for example, to minimize bleeding in the sternum duringan open-chest procedure.

[0076] Although certain parts of this disclosure are directedspecifically to creating incisions for accessing a patient's thoraciccavity and the harvesting and dissection of blood vessels within thebody during a CABG procedure, systems and methods of the invention areequally applicable to other procedures involving other organs or tissuesof the body, including minimally invasive procedures (e.g., minimallyinvasive CABG procedures), other open procedures, intravascularprocedures, urological procedures, laparascopy, arthroscopy,thoracoscopy or other cardiac procedures, cosmetic surgery, orthopedics,gynecology, otorhinolaryngology, spinal and neurologic procedures,oncology, and the like.

[0077] In methods of the present invention, high frequency (RF)electrical energy is usually applied to one or more active electrodes inthe presence of an electrically conductive fluid to remove and/or modifytarget tissue, an organ, or a body structure. Depending on the specificprocedure, the present invention may be used to: (1) create incisions intissue; (2) dissect or harvest tissue; (3) volumetrically remove tissueor cartilage (i.e., ablate or effect molecular dissociation of thetissue); (4) cut, transect, or resect tissue or an organ (e.g., a bloodvessel); (5) create perforations or holes within tissue; and/or (6)coagulate blood and severed blood vessels.

[0078] In one method of the present invention, the tissue structures areincised by volumetrically removing or ablating tissue along a cuttingpath. In this procedure, a high frequency voltage difference is appliedbetween one or more active electrode (s) and one or more returnelectrode(s) to develop high electric field intensities in the vicinityof the target tissue site. The high electric field intensities lead toelectric field induced molecular breakdown of target tissue throughmolecular dissociation (rather than thermal evaporation orcarbonization). Applicant believes that the tissue structure isvolumetrically removed through molecular disintegration of largerorganic molecules into smaller molecules and/or atoms, such as hydrogen,oxides of carbon, hydrocarbons and nitrogen compounds. This moleculardisintegration completely removes the tissue structure, as opposed todehydrating the tissue material by the removal of liquid within thecells of the tissue, as is typically the case with electrosurgicaldesiccation and vaporization.

[0079] The high electric field intensities may be generated by applyinga high frequency voltage that is sufficient to vaporize an electricallyconductive fluid over at least a portion of the active electrode(s) inthe region between the tip of the active electrode(s) and the targettissue. The electrically conductive fluid may be a gas or liquid, suchas isotonic saline, delivered to the target site, or a viscous fluid,such as a gel, that is located at the target site. In the latterembodiment, the active electrode(s) are submersed in the electricallyconductive gel during the surgical procedure. Since the vapor layer orvaporized region has a relatively high electrical impedance, itminimizes the current flow into the electrically conductive fluid.Within the vaporized fluid a plasma is formed, and charged particles(e.g., electrons) cause the localized molecular dissociation ordisintegration of components of the target tissue, to a depth of perhapsseveral cell layers. This molecular dissociation results in thevolumetric removal of tissue from the target site. This ablationprocess, which typically subjects the target tissue to a temperature inthe range of 40° C. to 70° C., can be precisely controlled to effect theremoval of tissue to a depth as little as about 10 microns, with littleor no thermal or other damage to surrounding tissue. This cool ablationphenomenon has been termed Coblation®.

[0080] While not being bound by theory, applicant believes that theprinciple mechanism of tissue removal in the Coblation® mechanism of thepresent invention is energetic electrons or ions that have beenenergized in a plasma adjacent to the active electrode(s). When a liquidis heated sufficiently that atoms vaporize from the liquid at a greaterrate than they recondense, a gas is formed. When the gas is heatedsufficiently that the atoms collide with each other and electrons areremoved from the atoms in the process, an ionized gas or plasma isformed. (A more complete description of plasmas (the so-called “fourthstate of matter”) can be found in Plasma Physics, by R. J. Goldston andP. H. Rutherford of the Plasma Physics Laboratory of PrincetonUniversity (1995), the complete disclosure of which is incorporatedherein by reference.) When the density of the vapor layer (or within abubble formed in the electrically conductive liquid) becomessufficiently low (i.e., less than approximately 10²⁰ atoms/cm³ foraqueous solutions), the electron mean free path increases to enablesubsequently injected electrons to cause impact ionization within theseregions of low density (i.e., vapor layers or bubbles). Once the ionicparticles in the plasma layer have sufficient energy, they acceleratetowards the target tissue. Energy evolved by the energetic electrons(e.g., 3.5 eV to 5 eV) can subsequently bombard a molecule and break itsbonds, dissociating a molecule into free radicals, which then combineinto final gaseous or liquid species.

[0081] Plasmas may be formed by heating and ionizing a gas by driving anelectric current through it, or by transmitting radio waves into thegas. Generally, these methods of plasma formation give energy to freeelectrons in the plasma directly, and then electron-atom collisionsliberate more electrons, and the process cascades until the desireddegree of ionization is achieved. Often, the electrons carry theelectrical current or absorb the radio waves and, therefore, are hotterthan the ions. Thus, in applicant's invention, the electrons, which arecarried away from the tissue towards the return electrode, carry most ofthe plasma's heat with them, allowing the ions to break apart the tissuemolecules in a substantially non-thermal manner.

[0082] The energy evolved by the energetic electrons may be varied byadjusting a variety of factors, such as: the number of activeelectrodes; electrode size and spacing; electrode surface area;asperities and sharp edges on the electrode surfaces; electrodematerials; applied voltage and power; current limiting means, such asinductors; electrical conductivity of the fluid in contact with theelectrodes; density of the fluid; electrical insulators over theelectrodes; and other factors. Accordingly, these factors can bemanipulated to control the energy level of the excited electrons. Sincedifferent tissue structures have different molecular bonds, the presentinvention can be configured to break the molecular bonds of certaintissue, while having too low an energy to break the molecular bonds ofother tissue. For example, fatty tissue, (e.g., adipose tissue) containsa large amount of lipid material having double bonds, the breakage ofwhich requires an energy level substantially higher than 4 eV to 5 eV.Accordingly, the present invention can be configured such that lipidcomponents of adipose tissue are selectively not ablated. Of course, thepresent invention may be used to effectively ablate cells of adiposetissue such that the inner fat content of the cells is released in aliquid form. Alternatively, the invention can be configured (e.g., byincreasing the voltage or changing the electrode configuration toincrease the current density at the electrode tips) such that the doublebonds of lipid materials are readily broken leading to moleculardissociation of lipids into low molecular weight condensable gases,generally as described hereinabove. A more complete description of theCoblation® phenomenon can be found in commonly assigned U.S. Pat. No.5,683,366 and co-pending U.S. patent application Ser. No. 09/032,375,filed Feb. 27, 1998 (Attorney Docket No. CB-3), the complete disclosuresof which are incorporated herein by reference.

[0083] Methods of the present invention typically involve theapplication of high frequency (RF) electrical energy to one or moreactive electrodes in the presence of an electrically conductive fluid toremove (i.e., resect, incise, perforate, cut, or ablate) a targettissue, structure, or organ; and/or to seal transected vessels withinthe region of the target tissue. The present invention is particularlyuseful for sealing larger arterial vessels, e.g., having a diameter onthe order of 1 mm or greater. In some embodiments, a high frequencypower supply is provided having an ablation mode, wherein a firstvoltage is applied to an active electrode sufficient to effect moleculardissociation or disintegration of the tissue; and a coagulation mode,wherein a second, lower voltage is applied to an active electrode(either the same or a different electrode) sufficient to achievehemostasis of severed vessels within the tissue. In other embodiments,an electrosurgical probe is provided having one or more coagulationelectrode(s) configured for sealing a severed vessel, such as anarterial vessel, and one or more active electrodes configured for eithercontracting the collagen fibers within the tissue or removing (ablating)the tissue, e.g., by applying sufficient energy to the tissue to effectmolecular dissociation. In the latter embodiments, the coagulationelectrode(s) may be configured such that a single voltage can be appliedto both coagulate with the coagulation electrode(s), and to ablate orcontract tissue with the active electrode(s). In other embodiments, thepower supply is combined with the coagulation probe such that thecoagulation electrode is used when the power supply is in thecoagulation mode (low voltage), and the active electrode(s) are usedwhen the power supply is in the ablation mode (higher voltage).

[0084] In one method of the present invention, one or more activeelectrodes are brought into close proximity to tissue at a target site,and the power supply is activated in the ablation mode such thatsufficient voltage is applied between the active electrodes and thereturn electrode to volumetrically remove the tissue through moleculardissociation, as described above. During this process, vessels withinthe tissue are severed. Smaller vessels may be automatically sealed withthe system and method of the present invention. Larger vessels and thosewith a higher flow rate, such as arterial vessels, may not beautomatically sealed in the ablation mode. In these cases, the severedvessels may be sealed by actuating a control (e.g., a foot pedal) toreduce the voltage of the power supply into the coagulation mode. Inthis mode, the active electrodes may be pressed against the severedvessel to provide sealing and/or coagulation of the vessel.Alternatively, a coagulation electrode located on the same or adifferent probe may be pressed against the severed vessel. Once thevessel is adequately sealed, the surgeon may activate a control (e.g.,another foot pedal) to increase the voltage of the power supply backinto the ablation mode.

[0085] The present invention is also useful for removing or ablatingtissue around nerves, such as spinal, or cranial nerves, e.g., thehypoglossal nerve, the optic nerve, facial nerves, vestibulocochlearnerves and the like. This is particularly advantageous when removingtissue that is located close to nerves. One of the significant drawbackswith the conventional RF devices, scalpels, and lasers is that thesedevices do not differentiate between the target tissue and thesurrounding nerves or bone. Therefore, the surgeon must be extremelycareful during these procedures to avoid damage to the nerves within andaround the target tissue. In the present invention, the Coblation®process for removing tissue results in no, or extremely small amounts,of collateral tissue damage, as described above. This allows the surgeonto remove tissue close to a nerve without causing collateral damage tothe nerve fibers and surrounding tissue.

[0086] In addition to the generally precise nature of the novelmechanisms of the present invention, applicant has discovered anadditional method of ensuring that adjacent nerves are not damagedduring tissue removal. According to the present invention, systems andmethods are provided for distinguishing between the fatty tissueimmediately surrounding nerve fibers and the normal tissue that is to beremoved during the procedure. Peripheral nerves usually comprise aconnective tissue sheath, or epineurium, enclosing the bundles of nervefibers, each bundle being surrounded by its own sheath of connectivetissue (the perineurium) to protect these nerve fibers. The outerprotective tissue sheath or epineurium typically comprises a fattytissue (e.g., adipose tissue) having substantially different electricalproperties than the normal target tissue that is treated. The system ofthe present invention measures the electrical properties of the tissueat the tip of the probe with one or more active electrode(s). Theseelectrical properties may include electrical conductivity at one,several, or a range of frequencies (e.g., in the range from 1 kHz to 100MHz), dielectric constant, capacitance or combinations of these. In thisembodiment, an audible signal may be produced when the sensingelectrode(s) at the tip of the probe detects the fatty tissuesurrounding a nerve, or direct feedback control can be provided to onlysupply power to the active electrode(s) either individually or to thecomplete array of electrodes, if and when the tissue encountered at thetip or working end of the probe is normal tissue based on the measuredelectrical properties.

[0087] In one embodiment, the current limiting elements are configuredsuch that the active electrodes will shut down or turn off when theelectrical impedance reaches a threshold level. When this thresholdlevel is set to the impedance of the fatty tissue surrounding nerves,the active electrodes will shut off whenever they come in contact with,or in close proximity to, nerves. Meanwhile, the other activeelectrodes, which are in contact with or in close proximity to targettissue, will continue to conduct electric current to the returnelectrode. This selective ablation or removal of lower impedance tissuein combination with the Coblation® mechanism of the present inventionallows the surgeon to precisely remove tissue around nerves or bone.Applicant has found that the present invention is capable ofvolumetrically removing tissue closely adjacent to nerves withoutimpairing the function of the nerves, and without significantly damagingthe tissue of the epineurium.

[0088] The present invention can be also be configured to create anincision in a bone of the patient. For example, the systems of thepresent invention can be used to create an incision in the sternum foraccess to the thoracic cavity. Applicant has found that the Coblation®mechanism of the present invention allows the surgeon to preciselycreate an incision in the sternum while minimizing or preventing bonebleeding. The high frequency voltage is applied between the activeelectrode(s) and the return electrode(s) to volumetrically remove thebone from a specific site targeted for the incision. As the activeelectrode(s) are passed through the incision in the bone, the sides ofthe active electrodes (or a third coagulation electrode) slidinglycontact the bone surrounding the incision to provide hemostasis in thebone. A more complete description of such coagulation electrodes can befound in U.S. patent application Ser. No. 09/162,117, filed Sep. 28,1998, the complete disclosure of which is incorporated herein byreference.

[0089] The present invention can also be used to dissect and harvestblood vessels from the patient's body during a CABG procedure. Thesystem of the present invention allows a surgeon to dissect and harvestblood vessels, such as the right or left IMA or saphenous vein, whileconcurrently providing hemostasis at the harvesting site. In someembodiments, a first high frequency voltage, can be delivered in anablation mode to effect molecular disintegration of connective tissueadjacent to the blood vessel targeted for harvesting; and a second,lower voltage can be delivered to achieve hemostasis of the connectivetissue adjacent to the blood vessel. In other embodiments, the targetedblood vessel can be transected at one or more positions along itslength, and one or more coagulation electrode(s) can be used to seal thetransected blood vessel at the site of transection. The coagulationelectrode(s) may be configured such that a single voltage can be appliedto the active electrodes to ablate the tissue and to coagulate the bloodvessel and target site.

[0090] The present invention also provides systems, apparatus, andmethods for selectively removing tumors or other undesirable bodystructures while minimizing the spread of viable cells from the tumor.Conventional techniques for removing such tumors generally result in theproduction of smoke in the surgical setting, termed an electrosurgicalor laser plume, which can spread intact, viable bacterial or viralparticles from the tumor or lesion to the surgical team, or viablecancerous cells to other locations within the patient's body. Thispotential spread of viable cells or particles has resulted in increasedconcerns over the proliferation of certain debilitating and fataldiseases, such as hepatitis, herpes, HIV and papillomavirus. In thepresent invention, high frequency voltage is applied between the activeelectrode(s) and one or more return electrode(s) to volumetricallyremove at least a portion of the tissue cells in the tumor or lesion bythe molecular dissociation of tissue components into non-condensablegases. The high frequency voltage is preferably selected to effectcontrolled removal of these tissue cells while minimizing substantialtissue necrosis to surrounding or underlying tissue. A more completedescription of this phenomenon can be found in co-pending U.S. patentapplication Ser. No. 09/109,219, filed Jun. 30, 1998 (Attorney DocketNo. CB-1), the complete disclosure of which is incorporated herein byreference.

[0091] A current flow path between the active electrode(s) and thereturn electrode(s) may be generated by submerging the tissue site in anelectrically conductive fluid (e.g., within a viscous fluid, such as anelectrically conductive gel) or by directing an electrically conductivefluid along a fluid path to the target site (i.e., a liquid, such asisotonic saline, or a gas, such as argon). This latter method isparticularly effective in a dry field procedure (i.e., the tissue is notsubmersed in fluid). The use of a conductive gel allows a slower, morecontrolled delivery rate of conductive fluid as compared with a liquidor a gas. In addition, the viscous nature of the gel may allow thesurgeon to more easily contain the gel around the target site (e.g., ascompared with containment of isotonic saline). A more completedescription of an exemplary method of directing electrically conductivefluid between the active and return electrodes is described in U.S. Pat.No. 5,697,281, the full disclosure of which is incorporated herein byreference. Alternatively, the body's natural conductive fluids, such asblood, may be sufficient to establish a conductive path between thereturn electrode(s) and the active electrode(s), and to provide theconditions for establishing a vapor layer, as described above. However,conductive fluid that is introduced into the patient is generallypreferred over blood because blood will tend to coagulate at certaintemperatures. Advantageously, a liquid electrically conductive fluid(e.g., isotonic saline) may be used to concurrently “bathe” the targettissue surface to provide an additional means for removing any tissue,and to cool the tissue at or adjacent to the target site.

[0092] In some embodiments of the invention, an electrosurgical probeincludes an electrode support for electrically isolating the activeelectrode(s) from the return electrode, and a fluid delivery port oroutlet for directing an electrically conductive fluid to the target siteor to the distal end of the probe. The electrode support and the fluidoutlet may be recessed from an outer surface of the instrument toconfine the electrically conductive fluid to the region immediatelysurrounding the electrode support. In addition, a shaft of theinstrument may be shaped so as to form a cavity around the electrodesupport and the fluid outlet. This helps to assure that the electricallyconductive fluid will remain in contact with the active electrode(s) andthe return electrode(s) to maintain the conductive path therebetween. Inaddition, this will help to maintain a vapor layer and subsequent plasmalayer between the active electrode(s) and the tissue at the treatmentsite throughout the procedure, thereby reducing any thermal damage thatmight otherwise occur if the vapor layer were extinguished due to a lackof conductive fluid. Provision of the electrically conductive fluidaround the target site also helps to maintain the tissue temperature atdesired levels.

[0093] The electrically conductive fluid should have a thresholdconductivity to provide a suitable conductive path between the returnelectrode and the active electrode(s). The electrical conductivity ofthe fluid (in units of milliSiemens per centimeter or mS/cm) willusually be greater than 0.2 mS/cm, preferably will be greater than 2mS/cm and more preferably greater than 10 mS/cm. In an exemplaryembodiment, the electrically conductive fluid is isotonic saline, whichhas a conductivity of about 17 mS/cm.

[0094] An electrosurgical probe or instrument of the invention typicallyincludes a shaft having a proximal end and a distal end, and one or moreactive electrode(s) disposed at the shaft distal end. The shaft servesto mechanically support the active electrode(s) and permits the treatingphysician to manipulate the shaft distal end via a handle attached tothe proximal end of the shaft. The shaft may be rigid or flexible, withflexible shafts optionally being combined with a generally rigidexternal tube for mechanical support. Flexible shafts may be combinedwith pull wires, shape memory actuators, and other known mechanisms foreffecting selective deflection of the distal end of the shaft tofacilitate positioning of the electrode array. The shaft will usuallyhave one or more wires, electrode connectors, leads, or other conductiveelements running axially therethrough, to permit connection of theelectrode(s) to a connection block located at the proximal end of theinstrument. The connection block is adapted for coupling theelectrode(s) to the power supply or controller. Typically, theconnection block is housed within the handle of the probe.

[0095] The shaft of an instrument under the invention may assume variousconfigurations. Generally, the shaft will have a suitable diameter andlength to allow the surgeon to access the target site with the distal orworking end of the shaft. Thus, the shaft may be provided in a range ofsizes according to the particular procedure or tissue targeted fortreatment. Typically, the shaft will have a length in the range of fromabout 5 cm to 30 cm, and have a diameter in the range of from about_(—)0.5 mm to 10 mm. Specific shaft designs will be described in detailin connection with the drawings hereinafter.

[0096] The present invention may use a single active electrode or aplurality of electrodes distributed across a contact surface of a probe(e.g., in a linear fashion). In the latter embodiment, the electrodearray usually includes a plurality of independently current-limitedand/or power-controlled active electrodes to apply electrical energyselectively to the target tissue while limiting the unwanted applicationof electrical energy to the surrounding tissue and environment resultingfrom power dissipation into surrounding electrically conductive liquids,such as blood, normal saline, electrically conductive gel and the like.The active electrodes may be independently current-limited by isolatingthe terminals from each other and connecting each terminal to a separatepower source that is isolated from the other active electrodes.Alternatively, the active electrodes may be connected to each other ateither the proximal or distal ends of the probe to form a single wirethat couples to a power source.

[0097] In one configuration, each individual active electrode iselectrically insulated from all other active electrodes within the probeand is connected to a power source which is isolated from each of theother active electrodes in the array, or to circuitry which limits orinterrupts current flow to the active electrode when low resistivitymaterial causes a low impedance path between the return electrode andthe individual active electrode. The isolated power sources for eachindividual active electrode may be separate power supply circuits havinginternal impedance characteristics which limit power to the associatedactive electrode when a low impedance return path is encountered. By wayof example, the isolated power source may be a user selectable constantcurrent source. In this embodiment, lower impedance paths willautomatically result in lower resistive heating levels since the heatingis proportional to the square of the operating current times theimpedance. Alternatively, a single power source may be connected to eachof the active electrodes through independently actuatable switches, orby independent current limiting elements, such as inductors, capacitors,resistors and/or combinations thereof. The current limiting elements maybe provided in the probe, connectors, cable, power supply or along theconductive path from the power supply to the distal tip of the probe.Alternatively, the resistance and/or capacitance may occur on thesurface of the active electrode(s) due to oxide layers which formselected active electrodes (e.g., titanium or a resistive coating on thesurface of metal, such as platinum).

[0098] The distal end of the probe may comprise many independent activeelectrodes designed to deliver electrical energy in the vicinity of thedistal end. The selective application of electrical energy to theconductive fluid is achieved by connecting each individual activeelectrode and the return electrode to a power source havingindependently controlled or current limited channels. The returnelectrode(s) may comprise a single tubular member of electricallyconductive material at the distal end of the probe proximal to theactive electrode(s) The same tubular member of electrically conductivematerial may also serve as a conduit for the supply of the electricallyconductive fluid between the active and return electrodes. Theapplication of high frequency voltage between the return electrode(s)and the active electrode(s) results in the generation of high electricfield intensities at the distal tip of the active electrode(s), withconduction of high frequency current from each active electrode to thereturn electrode. The current flow from each active electrode to thereturn electrode(s) is controlled by either active or passive means, ora combination thereof, to deliver electrical energy to the surroundingconductive fluid while minimizing energy delivery to surrounding(non-target) tissue.

[0099] The application of a suitable high frequency voltage between thereturn electrode(s) and the active electrode(s) for appropriate timeintervals effects cutting, removing, ablating, shaping, contracting orotherwise modifying the target tissue. In one embodiment, the tissuevolume over which energy is dissipated (i.e., over which a high currentdensity exists) may be precisely controlled, for example, by the use ofa multiplicity of small active electrodes whose effective diameters orprincipal dimensions range from about 5 mm to 0.01 mm, preferably fromabout 2 mm to 0.05 mm, and more preferably from about 1 mm to 0.1 mm.Electrode areas for both circular and non-circular terminals will have acontact area (per active electrode) below 25 mm², preferably being inthe range from 0.0001 mm² to 1 mm², and more preferably from 0.005 mm²to 0.5 mm². The circumscribed area of the electrode array is in therange from 0.25 mm² to 75 mm², preferably from 0.5 mm² to 40 mm². In oneembodiment the probe may include a plurality of relatively small activeelectrodes disposed over the distal contact surfaces on the shaft. Theuse of small diameter active electrodes increases the electric fieldintensity and reduces the extent or depth of tissue heating as aconsequence of the divergence of current flux lines which emanate fromthe exposed surface of each active electrode.

[0100] The portion of the electrode support on which the activeelectrode(s) are mounted generally defines a tissue treatment surface ofthe probe. The area of the tissue treatment surface can vary widely, andthe tissue treatment surface can assume a variety of geometries, withparticular areas and geometries being selected for specificapplications. The area of the tissue treatment surface can range fromabout 0.25 mm² to 75 mm², usually being from about 0.5 mm² to 40 mm².The geometries of the active electrode(s) can be planar, concave,convex, hemispherical, conical, a linear “in-line” array, or virtuallyany other regular or irregular shape. Most commonly, the activeelectrode(s) will be located at the shaft distal end of theelectrosurgical probe, frequently having planar, disk-shaped, orhemispherical surfaces for use in reshaping procedures, ablating,cutting, dissecting organs, coagulating, or transecting blood vessels.The active electrode(s) may be arranged terminally or laterally on theelectrosurgical probe (e.g., in the manner of a scalpel or a blade).However, it should be clearly understood that the active electrode ofthe invention does not cut or sever tissue mechanically as for a scalpelblade, but rather by the localized molecular dissociation of tissuecomponents due to application of high frequency electric current to theactive electrode. In one embodiment, a distal portion of the shaft maybe flattened or compressed laterally (e.g., FIGS. 32A-32C). A probehaving a laterally compressed shaft may facilitate access to certaintarget sites or body structures during various surgical procedures.

[0101] In embodiments having a plurality of active electrodes, it shouldbe clearly understood that the invention is not limited to electricallyisolated active electrodes. For example, a plurality of activeelectrodes may be connected to a single lead that extends through theprobe shaft and is coupled to a high frequency power supply.Alternatively, the probe may incorporate a single electrode that extendsdirectly through the probe shaft or is connected to a single lead thatextends to the power source. The active electrode may have a planar orblade shape, a screwdriver or conical shape, a sharpened point, a ballshape (e.g., for tissue vaporization and desiccation), a twizzle shape(for vaporization and needle-like cutting), a spring shape (for rapidtissue debulking and desiccation), a twisted metal shape, an annular orsolid tube shape, or the like. Alternatively, the electrode may comprisea plurality of filaments, a rigid or flexible brush electrode (fordebulking a tumor, such as a fibroid, bladder tumor or a prostateadenoma), a side-effect brush electrode on a lateral surface of theshaft, a coiled electrode, or the like.

[0102] In one embodiment, the probe comprises a single blade activeelectrode that extends from an insulating support member, spacer, orelectrode support, e.g., a ceramic or silicone rubber spacer located atthe distal end of the probe. The insulating support member may be atubular structure or a laterally compressed structure that separates theblade active electrode from a tubular or annular return electrodepositioned proximal to the insulating member and the active electrode.The blade electrode may include a distal cutting edge and sides whichare configured to coagulate the tissue as the blade electrode advancesthrough the tissue. In yet another embodiment, the catheter or probeincludes a single active electrode that can be rotated relative to therest of the catheter body, or the entire catheter may be rotatedrelative to the electrode lead(s). The single active electrode can bepositioned adjacent the abnormal tissue and energized and rotated asappropriate to remove or modify the target tissue.

[0103] The active electrode(s) are preferably supported within or by aninsulating support member positioned near the distal end of theinstrument shaft. The return electrode may be located on the instrumentshaft, on another instrument, or on the external surface of the patient(i.e., a dispersive pad). For certain procedures, the close proximity ofnerves and other sensitive tissue makes a bipolar design more preferablebecause this minimizes the current flow through non-target tissue andsurrounding nerves. Accordingly, the return electrode is preferablyeither integrated with the instrument body, or located on anotherinstrument. The proximal end of the probe typically includes theappropriate electrical connections for coupling the return electrode(s)and the active electrode(s) to a high frequency power supply, such as anelectrosurgical generator.

[0104] One exemplary power supply of the present invention delivers ahigh frequency current selectable to generate average power levelsranging from several milliwatts to tens of watts per electrode,depending on the volume of target tissue being treated, and/or themaximum allowed temperature selected for the instrument tip. The powersupply allows the user to select the voltage level according to thespecific requirements of a particular otologic procedure, neurosurgeryprocedure, cardiac surgery, arthroscopic surgery, dermatologicalprocedure, ophthalmic procedures, open surgery or other endoscopicsurgery procedure. For cardiac procedures and potentially forneurosurgery, the power source may have an additional filter, forfiltering leakage voltages at frequencies below 100 kHz, particularlyvoltages around 60 kHz. Alternatively, a power supply having a higheroperating frequency, e.g., 300 kHz to 500 kHz may be used in certainprocedures in which stray low frequency currents may be problematic. Adescription of one suitable power supply can be found in co-pendingpatent applications Ser. Nos. 09/058,571 and 09/058,336, filed Apr. 10,1998 (Attorney Docket Nos. CB-2 and CB-4), the complete disclosure ofboth applications are incorporated herein by reference for all purposes.

[0105] The voltage difference applied between the return electrode(s)and the active electrode(s) will be at high or radio frequency,typically between about 5 kHz and 20 MHz, usually being between about 30kHz and 2.5 MHz, preferably being between about 50 kHz and 500 kHz,often less than 350 kHz, and often between about 100 kHz and 200 kHz.The RMS (root mean square) voltage applied will usually be in the rangefrom about 5 volts to 1000 volts, preferably being in the range fromabout 10 volts to 500 volts depending on the active electrode size, theoperating frequency, and the operation mode of the particular procedureor desired effect on the tissue (e.g., contraction, coagulation, cuttingor ablation). Typically, the peak-to-peak voltage for ablation orcutting will be in the range of 10 volts to 2000 volts and preferably inthe range of 200 volts to 1800 volts , and more preferably in the rangeof about 300 volts to 1500 volts , often in the range of about 500 voltsto 900 volts peak to peak (again, depending on the electrode size, theoperating frequency and the operation mode). Lower peak-to-peak voltageswill be used for tissue coagulation or collagen contraction and willtypically be in the range from 50 to 1500, preferably 100 to 1000, andmore preferably 120 to 600 volts peak-to-peak.

[0106] The voltage is usually delivered in a series of voltage pulses oralternating current of time varying voltage amplitude with asufficiently high frequency (e.g., on the order of 5 kHz to 20 MHz) suchthat the voltage is effectively applied continuously (as compared withe.g., lasers claiming small depths of necrosis, which are generallypulsed about 10 Hz to 20 Hz). In addition, the duty cycle (i.e.,cumulative time in any one-second interval that energy is applied) is onthe order of about 50% for the present invention, as compared withpulsed lasers which typically have a duty cycle of about 0.0001%.

[0107] The power supply may include a fluid interlock for interruptingpower to the active electrode(s) when there is insufficient conductivefluid around the active electrode(s). This ensures that the instrumentwill not be activated when conductive fluid is not present, minimizingthe tissue damage that may otherwise occur. A more complete descriptionof such a fluid interlock can be found in commonly assigned, copendingU.S. application Ser. No. 09/058,336, filed Apr. 10, 1998 (attorneyDocket No. CB-4), the complete disclosure of which is incorporatedherein by reference.

[0108] The power supply may also be current limited or otherwisecontrolled so that undesired heating of the target tissue or surrounding(non-target) tissue does not occur. In a presently preferred embodimentof the present invention, current limiting inductors are placed inseries with each independent active electrode, where the inductance ofthe inductor is in the range of 10 uH to 50,000 uH, depending on theelectrical properties of the target tissue, the desired tissue heatingrate and the operating frequency. Alternatively, capacitor-inductor (LC)circuit structures may be employed, as described previously in U.S. Pat.No. 5,697,909, the complete disclosure of which is incorporated hereinby reference. Additionally, current limiting resistors may be selected.Preferably, these resistors will have a large positive temperaturecoefficient of resistance so that, as the current level begins to risefor any individual active electrode in contact with a low resistancemedium (e.g., saline irrigant or blood), the resistance of the currentlimiting resistor increases significantly, thereby minimizing the powerdelivery from the active electrode into the low resistance medium (e.g.,saline irrigant or blood).

[0109] In some procedures, it may also be necessary to retrieve oraspirate the electrically conductive fluid and/or the non-condensablegaseous products of ablation. In addition, it may be desirable toaspirate small pieces of tissue or other body structures that are notcompletely disintegrated by the high frequency energy, or other fluidsat the target site, such as blood, mucus, purulent fluid, the gaseousproducts of ablation, or the like. Accordingly, the system of thepresent invention may include one or more suction lumen(s) in theinstrument, or on another instrument, coupled to a suitable vacuumsource for aspirating fluids from the target site. In addition, theinvention may include one or more aspiration electrode(s) coupled to thedistal end of the suction lumen for ablating, or at least reducing thevolume of, non-ablated tissue fragments that are aspirated into thelumen. The aspiration electrode(s) function mainly to inhibit cloggingof the lumen that may otherwise occur as larger tissue fragments aredrawn therein. The aspiration electrode(s) may be different from theablation active electrode(s), or the same electrode(s) may serve bothfunctions. A more complete description of instruments incorporatingaspiration electrode(s) can be found in commonly assigned, co-pendingpatent application Ser. No. 09/010,382, filed Jan. 21, 1998, thecomplete disclosure of which is incorporated herein by reference.

[0110] During a surgical procedure, the distal end of the instrument andthe active electrode(s) may be maintained at a small distance away fromthe target tissue surface. This small spacing allows for the continuousflow of electrically conductive fluid into the interface between theactive electrode(s) and the target tissue surface. The continuous flowof the electrically conductive fluid helps to ensure that the thin vaporlayer will remain between the active electrode(s) and the tissuesurface. In addition, dynamic movement of the active electrode(s) overthe tissue site allows the electrically conductive fluid to cool thetissue underlying and surrounding the target tissue to minimize thermaldamage to this surrounding and underlying tissue. Accordingly, theelectrically conductive fluid may be cooled to facilitate the cooling ofthe tissue. Typically, the active electrode(s) will be about 0.02 mm to2 mm from the target tissue and preferably about 0.05 mm to 0.5 mmduring the ablation process. One method of maintaining this space is tomove, translate and/or rotate the probe transversely relative to thetissue, i.e., for the operator to use a light brushing motion, tomaintain a thin vaporized layer or region between the active electrodeand the tissue. Of course, if coagulation or collagen shrinkage of adeeper region of tissue is necessary (e.g., for sealing a bleedingvessel embedded within the tissue), it may be desirable to press theactive electrode(s) against the tissue to effect joulean heatingtherein.

[0111] Referring to FIG. 1, an exemplary electrosurgical system 11 forcutting, ablating, resecting, or otherwise modifying tissue will now bedescribed in detail. Electrosurgical system 11 generally comprises anelectrosurgical handpiece or probe 10 connected to a power supply 28 forproviding high frequency voltage to a target site, and a fluid source 21for supplying electrically conductive fluid 50 to probe 10. In addition,electrosurgical system 11 may include an endoscope (not shown) with afiber optic head light for viewing the surgical site. The endoscope maybe integral with probe 10, or it may be part of a separate instrument.The system 11 may also include a vacuum source (not shown) for couplingto a suction lumen or tube 211 (see FIG. 2) in the probe 10 foraspirating the target site.

[0112] As shown, probe 10 generally includes a proximal handle 19 and anelongate shaft 18 having one or more active electrodes 58 at its distalend. A connecting cable 34 has a connector 26 for electrically couplingthe active electrodes 58 to power supply 28. In embodiments having aplurality of active electrodes, active electrodes 58 are electricallyisolated from each other and the terminal of each active electrode 58 isconnected to an active or passive control network within power supply 28by means of a plurality of individually insulated conductors (notshown). A fluid supply tube 15 is connected to a fluid tube 14 of probe10 for supplying electrically conductive fluid 50 to the target site.

[0113] Power supply 28 has an operator controllable voltage leveladjustment 30 to change the applied voltage level, which is observableat a voltage level display 32. Power supply 28 also includes first,second, and third foot pedals 37, 38, 39 and a cable 36 which isremovably coupled to power supply 28. The foot pedals 37, 38, 39 allowthe surgeon to remotely adjust the energy level applied to activeelectrode(s) 58. In an exemplary embodiment, first foot pedal 37 is usedto place the power supply into the “ablation” mode and second foot pedal38 places power supply 28 into the “coagulation” mode. The third footpedal 39 allows the user to adjust the voltage level within the ablationmode. In the ablation mode, a sufficient voltage is applied to theactive electrodes to establish the requisite conditions for moleculardissociation of the tissue (i.e., vaporizing a portion of theelectrically conductive fluid, ionizing the vapor layer and acceleratingcharged particles against the tissue). As discussed above, the requisitevoltage level for ablation will vary depending on the number, size,shape and spacing of the electrodes, the distance in which theelectrodes extend from the support member, etc. When the surgeon isusing the power supply in the ablation mode, voltage level adjustment 30or third foot pedal 39 may be used to adjust the voltage level to adjustthe degree or aggressiveness of the ablation.

[0114] Of course, it will be recognized that the voltage and modality ofthe power supply may be controlled by other input devices. However,applicant has found that foot pedals are convenient means forcontrolling the power supply while manipulating the probe during asurgical procedure.

[0115] In the coagulation mode, the power supply 28 applies a low enoughvoltage to the active electrode(s) (or the coagulation electrode) toavoid vaporization of the electrically conductive fluid and subsequentmolecular dissociation of the tissue. The surgeon may automaticallytoggle the power supply between the ablation and coagulation modes byalternately stepping on foot pedals 37, 38, respectively. This allowsthe surgeon to quickly move between coagulation and ablation in situ,without having to remove his/her concentration from the surgical fieldor without having to request an assistant to switch the power supply. Byway of example, as the surgeon is sculpting soft tissue in the ablationmode, the probe typically will simultaneously seal and/or coagulationsmall severed vessels within the tissue. However, larger vessels, orvessels with high fluid pressures (e.g., arterial vessels) may not besealed in the ablation mode. Accordingly, the surgeon can simply step onfoot pedal 38, automatically lowering the voltage level below thethreshold level for ablation, and apply sufficient pressure onto thesevered vessel for a sufficient period of time to seal and/or coagulatethe vessel. After this is completed, the surgeon may quickly move backinto the ablation mode by stepping on foot pedal 37. A specific designof a suitable power supply for use with the present invention can befound in Provisional Patent Application No. 60/062,997, filed Oct. 23,1997 (Attorney Docket No. 16238-007400), previously incorporated hereinby reference.

[0116]FIG. 2 shows an electrosurgical probe 20 according to oneembodiment of the invention. Probe 20 may be used in conjunction with asystem similar or analogous to system 11 (FIG. 1). As shown in FIG. 2,probe 20 generally includes an elongated shaft 100 which may be flexibleor rigid, a handle 204 coupled to the proximal end of shaft 100 and anelectrode support member 102 coupled to the distal end of shaft 100.Shaft 100 may comprise a plastic material that is easily molded into theshape shown in FIG. 3, or shaft 100 may comprise an electricallyconductive material, usually a metal, such as tungsten, stainless steelalloys, platinum or its alloys, titanium or its alloys, molybdenum orits alloys, and nickel or its alloys. In the latter case (i.e., shaft100 is electrically conductive), probe 20 includes an electricallyinsulating jacket 108, which is typically formed as one or moreelectrically insulating sheaths or coatings, such aspolytetrafluoroethylene, polyimide, and the like. The provision ofelectrically insulating jacket 108 over shaft 100 prevents directelectrical contact between the metal shaft and any adjacent bodystructure or the surgeon. Such direct electrical contact between a bodystructure (e.g., heart, bone, nerves, skin, or other blood vessels) andan exposed electrode could result in unwanted heating and necrosis ofthe structure at the point of contact.

[0117] Handle 204 typically comprises a plastic material that is easilymolded into a suitable shape for handling by the surgeon. Handle 204defines an inner cavity (not shown) that houses an electricalconnections unit 250 (FIG. 5), and provides a suitable interface forcoupling probe 20 to power supply 28 via an electrical connecting cable.Electrode support member 102 extends from the distal end of shaft 100(usually about 1 mm to 20 mm), and provides support for an activeelectrode or a plurality of electrically isolated active electrodes 104.In the specific configuration shown in FIG. 2, probe 20 includes aplurality of active electrodes. As shown in FIG. 2, a fluid tube 233extends through an opening in handle 204, and includes a connector 235for connection to a fluid supply source for supplying electricallyconductive fluid to the target site. Fluid tube 233 is coupled to adistal fluid tube 239 that extends along the outer surface of shaft 100to an opening 237 at the distal end of the probe 20, as will bediscussed in detail below. Of course, the invention is not limited tothis configuration. For example, fluid tube 233 may extend through asingle lumen (not shown) in shaft 100, it may be coupled to a pluralityof lumens (also not shown) that extend through shaft 100 to a pluralityof openings at its distal end, or the fluid tube may be completelyindependent of shaft 100. Probe 20 may also include a valve orequivalent structure for controlling the flow rate of the electricallyconductive fluid to the target site.

[0118] As shown in FIGS. 3 and 4, electrode support member 102 has asubstantially planar tissue treatment surface 212 and comprises asuitable insulating material (e.g., a ceramic or glass material, such asalumina, zirconia and the like) which could be formed at the time ofmanufacture in a flat, hemispherical or other shape according to therequirements of a particular procedure. The preferred support membermaterial is alumina (Kyocera Industrial Ceramics Corporation, Elkgrove,Ill.), because of its high thermal conductivity, good electricallyinsulative properties, high flexural modulus, resistance to carbontracking, biocompatibility, and high melting point. Electrode supportmember 102 is adhesively joined to a tubular support member (not shown)that extends most or all of the distance between support member 102 andthe proximal end of probe 20. The tubular member preferably comprises anelectrically insulating material, such as an epoxy or silicone-basedmaterial.

[0119] In a preferred construction technique, active electrodes 104extend through pre-formed openings in the support member 102 so thatthey protrude above tissue treatment surface 212 by the desireddistance. The electrodes are then bonded to the tissue treatment surface212 of support member 102, typically by an inorganic sealing material.The sealing material is selected to provide effective electricalinsulation, and good adhesion to both support member 102 and activeelectrodes 104. In one embodiment, active electrodes 104 comprise anelectrically conducting, corrosion resistant metal, such as platinum ortitanium. The sealing material additionally should have a compatiblethermal expansion coefficient and a melting point well below that ofplatinum or titanium and alumina or zirconia, typically being a glass orglass ceramic.

[0120] In the embodiment shown in FIGS. 2-5, probe 20 includes a returnelectrode 112 for completing the current path between active electrodes104 and a high frequency power supply 28 (see FIG. 1). As shown, returnelectrode 112 preferably comprises an annular conductive band coupled tothe distal end of shaft 100 at a location proximal to tissue treatmentsurface 212 of electrode support member 102, typically about 0.5 mm to10 mm proximal to surface 212, and more preferably about 1 mm to 10 mmproximal to surface 212. Return electrode 112 is coupled to a connector258 that extends to the proximal end of probe 20, where it is suitablyconnected to power supply 28 (FIGS. 1 and 2).

[0121] As shown in FIG. 2, return electrode 112 is not directlyconnected to active electrodes 104. To complete this current path sothat active electrodes 104 are electrically connected to returnelectrode 112, electrically conductive fluid (e.g., isotonic saline) iscaused to flow therebetween. In the representative embodiment, theelectrically conductive fluid is delivered through an external fluidtube 239 to opening 237, as described above (FIGS. 2 and 4).Alternatively, the fluid may be continuously delivered by a fluiddelivery element (not shown) that is separate from probe 20.

[0122] In alternative embodiments, the fluid path may be formed in probe20 by, for example, an inner lumen or an annular gap between the returnelectrode and a tubular support member within shaft 100 (not shown).This annular gap may be formed near the perimeter of the shaft 100 suchthat the electrically conductive fluid tends to flow radially inwardtowards the target site, or it may be formed towards the center of shaft100 so that the fluid flows radially outward. In both of theseembodiments, a fluid source (e.g., a bag of fluid elevated above thesurgical site or having a pumping device), is coupled to probe 20 via afluid supply tube (not shown) that may or may not have a controllablevalve. A more complete description of an electrosurgical probeincorporating one or more fluid lumen(s) can be found in U.S. Pat. No.5,697,281, filed on Jun. 7, 1995, the complete disclosure of which isincorporated herein by reference.

[0123] Referring to FIGS. 3 and 4, the electrically isolated activeelectrodes 104 are preferably spaced from each other and aligned to forma linear array 105 of electrodes for cutting a substantially linearincision in the tissue. The tissue treatment surface and individualactive electrodes 104 will usually have dimensions within the ranges setforth above. Active electrodes 104 preferably have a distal edge 107 toincrease the electric field intensities around terminals 104, and tofacilitate cutting of tissue. Thus, active electrodes 104 have ascrewdriver shape in the representative embodiment of FIGS. 2-4. In onerepresentative embodiment, the tissue treatment surface 212 has acircular cross-sectional shape with a diameter in the range of about 1mm to 30 mm, usually about 2 mm to 20 mm. The individual activeelectrodes 104 preferably extend outward from tissue treatment surface212 by a distance of about 0.1 mm to 8 mm, usually about 1 mm to 4 mm.Applicant has found that this configuration increases the high electricfield intensities and associated current densities around activeelectrodes 104 to facilitate the ablation of tissue as described indetail above.

[0124] Probe 20 may include a suction or aspiration lumen 213 (see FIG.2) within shaft 100 and a suction tube 211 (FIG. 2) for aspiratingtissue, fluids and/or gases from the target site. In this embodiment,the electrically conductive fluid generally flows from opening 237 offluid tube 239 radially inward and then back through one or moreopenings (not shown) in support member 102. Aspirating the electricallyconductive fluid during surgery allows the surgeon to see the targetsite, and it prevents the fluid from flowing into the patient's body(e.g., the thoracic cavity). This aspiration should be controlled,however, so that the conductive fluid maintains a conductive pathbetween the active electrode(s) and the return electrode. In someembodiments, the probe 20 will also include one or more aspirationelectrode(s) (not shown) coupled to the aspiration lumen for inhibitingclogging during aspiration of tissue fragments from the surgical site. Amore complete description of these embodiments can be found in commonlyassigned co-pending U.S. patent application Ser. No. 09/010,382, filedJan. 21, 1998, the complete disclosure of which is incorporated hereinby reference for all purposes.

[0125]FIG. 5 illustrates the electrical connections 250 within handle204 for coupling active electrodes 104 and return electrode 112 to thepower supply 28. As shown, a plurality of wires 252 extend through shaft100 to couple electrodes 104 to a plurality of pins 254, which areplugged into a connector block 256 for coupling to a connecting cable 22(FIG. 1). Similarly, return electrode 112 is coupled to connector block256 via a wire 258 and a plug 260.

[0126] According to the present invention, probe 20 further includes anidentification element that is characteristic of the particularelectrode assembly so that the same power supply 28 can be used fordifferent electrosurgical operations. In one embodiment, for example,probe 20 includes a voltage reduction element or a voltage reductioncircuit for reducing the voltage applied between the active electrodes104 and the return electrode 112. The voltage reduction element servesto reduce the voltage applied by the power supply so that the voltagebetween the active electrodes and the return electrode is low enough toavoid excessive power dissipation into the electrically conductivemedium and/or the tissue at the target site. The voltage reductionelement primarily allows the electrosurgical probe 10/20 to becompatible with a range of different power supplies that are adapted toapply higher voltages for ablation or vaporization of tissue (e.g.,various power supplies or generators manufactured by ArthroCareCorporation, Sunnyvale, Calif.). For contraction of tissue, for example,the voltage reduction element will serve to reduce a voltage of about100 to 135 volts RMS (which corresponds to a setting of 1 on theArthroCare Model 970 and 980 (i.e., 2000) Generators) to about 45 to 60volts RMS, which is a suitable voltage for contraction of tissue withoutablation (e.g., molecular dissociation) of the tissue.

[0127] Again with reference to FIG. 5, n the representative embodimentthe voltage reduction element is a dropping capacitor 262 which has afirst leg 264 coupled to the return electrode wire 258 and a second leg266 coupled to connector block 256. Of course, the capacitor may belocated in other places within the system, such as in, or distributedalong the length of, the cable, the power supply, the connector, etc. Inaddition, it will be recognized that other voltage reduction elements,such as diodes, transistors, inductors, resistors, capacitors orcombinations thereof, may be used in conjunction with the presentinvention. For example, probe 20 may include a coded resistor (notshown) that is constructed to lower the voltage applied between returnelectrode 112 and active electrodes 104 to a suitable level forcontraction of tissue. In addition, electrical circuits may be employedfor this purpose.

[0128] Alternatively or additionally, the cable 22 that couples thepower supply 28 to probe 10/20 may be used as a voltage reductionelement. The cable has an inherent capacitance that can be used toreduce the power supply voltage if the cable is placed into theelectrical circuit between the power supply, the active electrodes andthe return electrode. In this embodiment, the cable 22 may be usedalone, or in combination with one of the voltage reduction elementsdiscussed above, e.g., a capacitor.

[0129] Further, it should be noted that various electrosurgical probesof the present invention can be used with a particular power supply thatis adapted to apply a voltage within a selected range for a certainprocedure or treatment. In which case, a voltage reduction element orcircuitry may not be necessary nor desired.

[0130] With reference to FIGS. 6-8, electrode support member 70according to one embodiment includes a multi-layer substrate comprisinga suitable high temperature, electrically insulating material, such asceramic. The multi-layer substrate is a thin or thick-film hybrid havingconductive strips that are adhered to the ceramic wafer layers (e.g.,thick-film printed and fired onto or plated onto the ceramic wafers).The conductive strips typically comprise tungsten, gold, nickel, silver,platinum or equivalent materials. In the exemplary embodiment, theconductive strips comprise tungsten, and they are co-fired together withthe wafer layers to form an integral package. The conductive strips arecoupled to external wire connectors by holes or vias that are drilledthrough the ceramic layers, and plated or otherwise covered withconductive material. A more complete description of such support members370 can be found in U.S. patent application Ser. No. 08/977,845, filedNov. 25, 1997 (Attorney Docket No. D-2), the entire disclosure of whichis incorporated herein by reference.

[0131] In the representative embodiment, support member 70 comprisesfive ceramic layers 200, 202, 204, 206, 208 (see FIGS. 6-10), three goldplated active electrodes 210 a, 210 b, 210 c and first and second goldplated return electrodes 216, 218. As shown in FIGS. 9A and 9B, a firstceramic layer 200, which is one of the outer layers of support 70,includes first gold plated return electrode 216 on a lateral surface 220of layer 200. First ceramic layer 200 further includes a gold conductivestrip 222 extending from return electrode 216 to the proximal end oflayer 200 for coupling to a lead wire (not shown), and three goldconductive lines 224, 226, 228 extending from a mid-portion of layer 200to its proximal end. Conductive strips 224, 226, 228 are each coupled toone of the active electrodes 210 a, 210 b, 210 c by conductive holes orvias 230, 232, 234, respectively. As shown, all three vias 230, 232, 234extend through wafer layer 200.

[0132] Referring to FIGS. 10A and 10B, a second wafer layer 202 isbonded between first outer wafer layer 200 and a middle wafer layer 204(See FIGS. 11A and 11B). As shown, first active electrode 210 a isattached to the distal surface of second wafer layer 202, and aconductive strip 240 extends to via 230 to couple active electrode 210 ato a lead wire. Similarly, wafer layers 204 and 206 (FIGS. 11A, 11B,12A, and 12B) each have an active electrode 210 b, 210 c plated to theirdistal surfaces, and a conductive strip 242, 244, respectively,extending to one of the vias 232, 234, respectively. Note that the viasonly extend as far as necessary through the ceramic layers. As shown inFIG. 13, a second outer wafer layer 208 has a second return electrode218 plated to the lateral surface 250 of layer 208. The second returnelectrode 218 is coupled directly to the first return electrode 216through a via 252 extending through the entire ceramic substrate.

[0133] Of course, it will be recognized that a variety of differenttypes of single layer and multi-layer wafers may be constructedaccording to the present invention. For example, FIGS. 14 and 15illustrate an alternative embodiment of the multi-layer ceramic wafer,wherein the active electrodes comprise planar strips 280 that are platedor otherwise bonded between the ceramic wafer layers 282. Each of theplanar strips 280 has a different length, as shown in FIG. 15, so thatthe active electrodes can be electrically isolated from each other, andcoupled to lead wires by vias (not shown).

[0134]FIG. 16 illustrates an electrosurgical probe 20′ according toanother embodiment of the present invention. Probe 20′ generallyincludes handle 104 attached to shaft 100, and has a single, thin,elongated active blade electrode 58. Active electrode 58 is mechanicallyand electrically separated from return electrode 112 by a supportstructure 102. The active blade electrode 58 has a sharp distal edge 59which helps facilitate the cutting process, and sides 62 which contactthe tissue (e.g., bone) as the blade electrode 58 passes through thetissue or body structure. By contacting the sides of the blade electrode58 directly with the tissue or body structure, the electrical powersupplied to electrode 58 by power supply 28 can provide hemostasis tothe body structure during the cutting process. Optionally, probe 20′ canfurther include one or more coagulation electrode(s) (not shown)configured to seal a severed vessel, bone, or other tissue that is beingincised. Such coagulation electrode(s) may be configured such that asingle voltage can be applied to coagulate with the coagulationelectrode(s) while ablating tissue with the active electrode(s).According to one aspect of the invention, probe 20′ is particularlyuseful for creating an incision in a patient's chest. For example, in anopen-chest CABG procedure a median sternotomy is first performed inwhich the sternum is sectioned longitudinally so as to allow the chestto be opened for access to the thoracic cavity. Active electrodes 58include distal edge 59 suitable for sectioning the sternum, and sides 62suitable for arresting bone bleeding within the incised sternum. Sides62 are configured to slidably engage the sternum as active electrode 58is moved with respect to the sternum. Return electrode 112 is spacedproximally from active electrode 58 such that the electrical current isdrawn away from the surrounding tissue. Alternatively, the returnelectrode 112 may be a dispersive pad located on the external surface ofthe patient's body. By minimizing bleeding of the sternum during anopen-chest procedure, the patient's recovery time can be substantiallyshortened and patient suffering is alleviated.

[0135] FIGS. 17A-17C schematically illustrate the distal portion ofthree different embodiments of a probe 90 according to the presentinvention. As shown in FIG. 17A, active electrodes 104 are anchored in asupport 102 of suitable insulating material (e.g., ceramic or glassmaterial, such as alumina, zirconia and the like) which could be formedat the time of manufacture in a flat, hemispherical or other shapeaccording to the requirements of a particular procedure. In oneembodiment, the support material is alumina, available from KyoceraIndustrial Ceramics Corporation, Elkgrove, Ill., because of its highthermal conductivity, good electrically insulative properties, highflexural modulus, resistance to carbon tracking, biocompatibility, andhigh melting point. The support 102 is adhesively joined to a tubularsupport member 78 that extends most or all of the distance betweenmatrix 102 and the proximal end of probe 90. Tubular member 78preferably comprises an electrically insulating material, such as anepoxy or silicone-based material.

[0136] According to one construction technique, active electrodes 104extend through pre-formed openings in the support 102 so that theyprotrude above tissue treatment surface 212 by the desired distance. Theelectrodes are then bonded to the tissue treatment surface 212 ofsupport 102, typically by an inorganic sealing material 80. Sealingmaterial 80 is selected to provide effective electrical insulation, andgood adhesion to both the support 102 and the platinum or titaniumactive electrodes. Sealing material 80 additionally should have acompatible thermal expansion coefficient, and a melting point well belowthat of platinum or titanium and alumina or zirconia, typically being aglass or glass ceramic.

[0137] In the embodiment shown in FIG. 17A, return electrode 112comprises an annular member positioned around the exterior of shaft 100of probe 90. Return electrode 112 may fully or partially circumscribetubular member 78 to form an annular gap 54 therebetween for flow ofelectrically conductive liquid 50 therethrough, as discussed below. Gap54 preferably has a width in the range of 0.25 mm to 4 mm.Alternatively, probe 90 may include a plurality of longitudinal ribsbetween tubular member 78 and return electrode 112 to form a pluralityof fluid lumens extending along the perimeter of shaft 100. In thisembodiment, the plurality of lumens will extend to a plurality ofopenings.

[0138] Return electrode 112 is disposed within an electricallyinsulative jacket 17, which is typically formed as one or moreelectrically insulative sheaths or coatings, such aspolytetrafluoroethylene, polyimide, and the like. The provision of theelectrically insulative jacket 17 over return electrode 112 preventsdirect electrical contact between return electrode 112 and any adjacentbody structure. Such direct electrical contact between a body structure(e.g., the heart) and an exposed electrode member 112 could result inunwanted heating and necrosis of the structure at the point of contact.

[0139] As shown in FIG. 17A, return electrode 112 is not directlyconnected to active electrodes 104. To complete a current path so thatactive electrodes 104 are electrically connected to return electrode112, electrically conductive liquid 50 (e.g., isotonic saline) is causedto flow along fluid path(s) 83. Fluid path 83 is formed by annular gap54 between outer return electrode 112 and tubular support member 78. Theelectrically conductive liquid 50 flowing through fluid path 83 providesa pathway for electrical current flow between active electrodes 104 andreturn electrode 112, as illustrated by the current flux lines 60 inFIG. 17A. When a voltage difference is applied between active electrodes104 and return electrode 112, high electric field intensities will begenerated at the distal tips of active electrodes 104 with current flowfrom electrodes 104 through the target tissue to the return electrode,the high electric field intensities causing ablation of tissue 52 inzone 88.

[0140]FIG. 17B illustrates another alternative embodiment ofelectrosurgical probe 90 which has a return electrode 112 positionedwithin tubular member 78. Return electrode 112 may comprise a tubularmember defining an inner lumen 57 for allowing electrically conductiveliquid 50 (e.g., isotonic saline) to flow therethrough in electricalcontact with return electrode 112. In this embodiment, a voltagedifference is applied between active electrodes 104 and return electrode112 resulting in electrical current flow through the electricallyconductive liquid 50 as shown by current flux lines 60. As a result ofthe applied voltage difference and concomitant high electric fieldintensities at the tips of active electrodes 104, tissue 52 becomesablated or transected in zone 88.

[0141]FIG. 17C illustrates another embodiment of probe 90 that is acombination of the embodiments in FIGS. 17A and 17B. As shown, thisprobe includes both an inner lumen 57 and an outer gap or plurality ofouter lumens 54 for flow of electrically conductive fluid. In thisembodiment, the return electrode 112 may be positioned within tubularmember 78 as in FIG. 17B, outside of tubular member 78 as in FIG. 17A,or in both locations.

[0142]FIG. 18 illustrates another embodiment of probe 90 where thedistal portion of shaft 100 is bent so that active electrodes extendtransversely to the shaft. Preferably, the distal portion of shaft 100is perpendicular to the rest of the shaft so that tissue treatmentsurface 212 is generally parallel to the shaft axis. In this embodiment,return electrode 112 is mounted to the outer surface of shaft 100 and iscovered with an electrically insulating jacket 17. The electricallyconductive fluid 50 flows along flow path 83 through return electrode112 and exits the distal end of electrode 112 at a point proximal oftissue treatment surface 212. The fluid is directed exterior of shaft tosurface 212 to create a return current path from active electrodes 104,through the fluid 50, to return electrode 112, as shown by current fluxlines 60.

[0143]FIG. 19 illustrates another embodiment of the invention whereelectrosurgical system 11 further includes a liquid supply instrument 64for supplying electrically conductive fluid 50 between active electrodes104 and a return electrode 112′. Liquid supply instrument 64 comprisesan inner tubular member or return electrode 112′ surrounded by anelectrically insulating jacket 17. Return electrode 112′ defines aninner passage 83 for flow of fluid 50. As shown in FIG. 19, the distalportion of instrument 64 is preferably bent so that liquid 50 isdischarged at an angle with respect to instrument 64. This allows thesurgical team to position liquid supply instrument 64 adjacent tissuetreatment surface 212 with the proximal portion of supply instrument 64oriented at a similar angle to probe 90.

[0144] The present invention is not limited to an electrode arraydisposed on a relatively planar surface at the distal tip of probe 90,as described above. Referring to FIGS. 20A and 20B, an alternative probe90 includes a pair of electrodes 105 a, 105 b mounted to the distal endof shaft 100. Electrodes 105 a, 105 b are electrically connected to apower supply, as described above, and preferably have tips 107 a, 107 bhaving a screwdriver shape. The screwdriver shape provides a greateramount of “edges” to electrodes 105 a, 105 b, to increase the electricfield intensity and current density at tips 107 a, 107 b, therebyimproving the cutting ability as well as the ability to providehemostasis of the incised tissue.

[0145]FIG. 21 illustrates yet another embodiment designed for cutting ofbody tissue, organs, or structures. In this embodiment, the activeelectrodes 104 are arranged in a linear or columnar array of one of moreclosely spaced columns so that as the electrodes 104 are moved along thelonger axis (denoted by arrow 160 in FIG. 21), the current flux linesare narrowly confined at the tip of the active electrodes 104 and resultin a cutting effect in the body structure being treated. As before, thecurrent flux lines 60 emanating from the active electrodes 104 passthrough the electrically conductive liquid to the return electrodestructure 112 located proximal to the probe tip.

[0146] Referring now to FIGS. 22 and 23, alternative geometries areshown for the active electrodes 104. These alternative electrodegeometries allow the electrical current densities emanating from theactive electrodes 104 to be concentrated to achieve an increasedablation rate and/or a more concentrated ablation effect due to the factthat sharper edges (i.e., regions of smaller radii of curvature) resultin higher current densities. FIG. 22 illustrates a flattened extensionof a round wire active electrode 104 which results in higher currentdensities at the edges 180. Another example is shown in FIG. 23 in whichthe active electrode 104 is formed into a cone shaped point 182resulting in higher current densities at the tip of the cone.

[0147] Another embodiment of the electrosurgical probe is illustrated inFIG. 24. The electrosurgical probe 90 comprises a shaft 100 and at leasttwo active electrodes 104 extending from a support 102 at the distal endof the shaft. The active electrodes 104 preferably define a distal edge600 for making an incision in tissue. The edges 600 of the activeelectrodes 104 are substantially parallel with each other and usuallyspaced a distance of about 4 mm to 15 mm apart, preferably about 8 mm to10 mm apart. The edges 600 extend from the distal end of support 102 bya distance of about 0.5 mm to 10 mm, preferably about 2 mm to 5 mm. Inthe exemplary embodiment, probe 90 will include a return electrode 112spaced proximally from the active electrodes 104. In an alternativeembodiment (not shown), one of the active electrodes 104 may function asa return electrode, or the return electrode may be a dispersive padlocated on an external surface of the patient's body.

[0148]FIG. 25 illustrates a distal portion of an electrosurgical probe500 according to another embodiment of the present invention Theembodiment of FIG. 25 is particularly useful for cutting or creatingincisions in tissue structures. Probe 500 comprises a support member 502coupled to a shaft or disposable tip (not shown) as described inprevious embodiments. Support member 502 preferably comprises aninorganic electrically insulating material, such as ceramic, glass orglass-ceramic. In this embodiment, however, support member 502 maycomprise an organic material, such as plastic, because the activeelectrode 506 and return electrode 508 are both spaced away from supportmember 502. Thus, the high intensity electric fields may be far enoughaway from support member 502 so as to allow an organic material.

[0149] An electrode assembly 504 extends from a distal end of supportmember 502, preferably by a distance of about 2 mm to 20 mm. Electrodeassembly 504 comprises a single, active electrode 506 and a returnelectrode sleeve 508 spaced proximally from active electrode 506 by aninsulation member 510, which preferably comprises an inorganic material,such as ceramic, glass or glass-ceramic. As shown, active electrode 506preferably tapers to a sharp distal end 512 to facilitate the cutting orincising of tissue. In the exemplary embodiment, active electrode 506has a proximal diameter of about 0.2 to 20 mm and a distal diameter ofless than about 0.2 mm. Return electrode 508 is spaced from activeelectrode 506 a sufficient distance to prevent shorting or arcingtherebetween at sufficient voltages to allow the volumetric removal oftissue. In the representative embodiment, the distal exposed portion ofreturn electrode 508 is spaced about 0.5 to about 5 mm from the proximalexposed portion of active electrode 506. Of course, it will berecognized that the present invention is not limited to the particulardimensions and configuration of the electrode assembly 504 describedherein, and a variety of different configurations may be envisioneddepending on the surgical application.

[0150] As shown, probe 500 includes a fluid lumen 520 passing throughsupport member 502 to a distal opening (not shown) at the distal end ofsupport member 502. Fluid lumen 520 is coupled to a supply ofelectrically conductive fluid, such as isotonic saline, or othersuitable conductive fluid for delivery of such fluid to the target site.In the exemplary embodiment, probe 500 is designed such that lumen 520will be positioned above electrode assembly 504 during use such that theconductive fluid exiting the distal opening of lumen 520 will naturallypass over return electrode 508 and active electrode 506 thereby creatinga current path therebetween. In addition, the conductive fluid will besufficient to cover the active electrode 506 such that the conditionsfor plasma formation can be met, as described in detail above.

[0151] FIGS. 26, and 27A-C illustrate another exemplary electrosurgicalprobe 310 for cutting, incising, or removing tissue structures. Probe310 comprises a shaft or disposable tip 313 removably coupled to aproximal handle 312, and an electrically insulating electrode supportmember 370 extending from tip 313 for supporting a plurality of activeelectrodes 358. Tip 313 and handle 312 typically comprise a plasticmaterial that is easily molded into a suitable shape for handling by thesurgeon. As shown in FIGS. 27A and 27B, handle 312 defines an innercavity 372 that houses the electrical connections 374, and provides asuitable interface for connection to electrical connecting cable 34 (seeFIG. 1). In the exemplary embodiment, handle 312 is constructed of asteam autoclavable plastic or metal (e.g., polyethylether ketone, or astable metal alloy containing aluminum and/or zince) so that it can bere-used by sterilizing handle 312 between surgical procedures. Highservice temperature materials are preferred, such as a silicone cablejacket and a poly-ether-imide handpiece or ULTEM® that can withstandrepeated exposure to high temperatures.

[0152] Referring to FIGS. 27A-27C, tip 313 preferably comprises firstand second housing halves 500, 502 that snap fit together, and form arecess 404 therebetween for holding electrode support member 370 withinthe tip 313. Electrode support member 370 extends from the distal end oftip 313, usually by about 0.5 mm to 20 mm, and provides support for aplurality of electrically isolated active electrodes 358 and one or morereturn electrodes 400. Alternatively, electrode support member 370 maybe recessed from the distal end of tip 313 to help confine theelectrically conductive fluid around the active electrodes 358 duringthe surgical procedure, as discussed above. Electrode support member 370has a substantially planar tissue treatment surface 380 that is usuallydisposed at an angle of about 10 to 90 degrees relative to thelongitudinal axis of handle 312 to facilitate handling by the surgeon.In the exemplary embodiment, this function is accomplished by orientingtip 313 at an acute angle relative to the longitudinal axis of handle312.

[0153] In the embodiment shown in FIGS. 26-27C, probe 310 includes asingle annular return electrode 400 for completing the current pathbetween active electrodes 358 and power supply 28 (see FIG. 1). Asshown, return electrode 400 preferably has a fluid contact surfaceslightly proximal to tissue treatment surface 380, typically by about0.1 mm to 2 mm, and preferably by about 0.2 mm to 1 mm. Return electrode400 is coupled to a connector 404 that extends to the proximal end ofhandle 313, where it is suitably connected to power supply 28 (FIG. 1).

[0154] Referring again to FIGS. 27A-27C, tip 313 further includes aproximal hub 506 for supporting a male electrical connector 508 thatholds a plurality of wires 510 each coupled to one of the activeelectrodes 358 or to return electrode 400 on support member 370. Afemale connector 520 housed within handle 312 is removably coupled tomale connector 508, and a plurality of wires 522 extend from femaleconnector 520 through a strain relief 524 to cable 334. Both sets ofwires 510, 522 are insulated to prevent shorting in the event of fluidingress into the probe 310. This design allows for removable connectionof the electrodes in tip 313 with the connector 520 within handle 312 sothat the handle can be re-used with different tips 313. Probe 310 willpreferably also include an identification element, such as a codedresistor (not shown), for programming a particular voltage output rangeand mode of operation for the power supply. This allows the power supplyto be employed with a variety of different probes for a variety ofdifferent applications.

[0155] In the representative embodiment, probe 310 includes a fluid tube410 (FIG. 26) for delivering electrically conductive fluid to the targetsite. Fluid tube 410 is sized to extend through a groove 414 in handle313 and through an inner cavity 412 in tip 312 to a distal opening 414(FIG. 26) located adjacent electrode support member 370. Tube 410extends all the way through inner cavity 412 to opening 414 to eliminateany possible fluid ingress into cavity 412. Fluid tube 410 includes aproximal connector for coupling to an electrically conductive fluidsource 321.

[0156] Probe 310 will also include a valve or equivalent structure forcontrolling the flow rate of the electrically conductive fluid to thetarget site. In the representative embodiment shown in FIGS. 27A-27C,handle 312 comprises a main body 422 coupled between distal hub 418 andstrain relief 420, and a rotatable sleeve 416 around main body 422.Distal hub 418 has an opening 419 for receiving proximal hub 506 of tip313 for removably coupling the tip 313 to the handle 312. Sleeve 416 isrotatably coupled to strain relief 420 and distal hub 418 to provide avalve structure for fluid tube 410. As shown in FIG. 27A, fluid tube 410extends through groove 414 from strain relief 420, through main body 422and distal hub 420 to tip 313. Rotation of sleeve 416 will impede, andeventually obstruct, the flow of fluid through tube 410. Of course, thisfluid control may be provided by a variety of other input and valvedevices, such as switches, buttons, etc.

[0157] In alternative embodiments, the fluid path may be directly formedin probe 310 by, for example, a central inner lumen or an annular gap(not shown) within the handle and the tip. This inner lumen may beformed near the perimeter of the probe 310 such that the electricallyconductive fluid tends to flow radially inward towards the target site,or it may be formed towards the center of probe 310 so that the fluidflows radially outward. In addition, the electrically conductive fluidmay be delivered from a fluid delivery element (not shown) that isseparate from probe 310. In arthroscopic surgery, for example, the bodycavity will be flooded with isotonic saline and the probe 310 will beintroduced into this flooded cavity. Electrically conductive fluid willbe continually resupplied to maintain the conduction path between returnelectrode 400 and active electrodes 358. A more complete description ofalternative electrosurgical probes incorporating one or more fluidlumen(s) can be found in commonly assigned, co-pending application Ser.No. 08/485,219, filed on Jun. 7, 1995 (Attorney Docket 16238-000600),the complete disclosure of which is incorporated herein by reference.

[0158] Referring now to FIG. 26, electrically isolated active electrodes358 are spaced apart over tissue treatment surface 380 of electrodesupport member 370, preferably in a linear array. In the representativeembodiment, three active electrodes 358, each having a substantiallyconical shape, are arranged in a linear array extending distally fromsurface 380. Active electrodes 358 will usually extend a distance ofabout 0.5 mm to 20 mm from tissue treatment surface 380, preferablyabout 1 mm to 5 mm. Applicant has found that this configurationincreases the electric field intensities and associated currentdensities at the distal edges of active electrodes 358, which increasesthe rate of tissue cutting. In the representative embodiment, the tissuetreatment surface 380 has a circular cross-sectional shape with adiameter in the range of about 0.5 mm to 20 mm (preferably about 2 mm to10 mm). The individual active electrodes 358 preferably taper outward asshown, or they may form a distal edge, such as the electrodes shown inFIGS. 3 and 24.

[0159] Probe 430 of FIG. 28 includes a shaft 432 coupled to a proximalhandle 434 for holding and controlling shaft 432. Probe 430 includes anactive electrode array 436 at the distal tip of shaft 432, an annularreturn electrode 438 extending through shaft 432 and proximally recessedfrom the active electrode array 436, and an annular lumen 442 betweenreturn electrode 438 and an outer insulating sheath 446. Probe 430further includes a liquid supply conduit 444 attached to handle 434 andin fluid communication with lumen 442, and a source of electricallyconductive fluid (not shown) for delivering the fluid past returnelectrode 438 to the target site on the tissue 440. Electrode array 436is preferably flush with the distal end of shaft 432 or distallyextended from the distal end by a small distance (on the order of 0.005inches) so as to minimize the depth of ablation. Preferably, the distalend of shaft 432 is beveled to improve access and control of probe 430while treating the target tissue.

[0160] Yet another embodiment of the present invention is shown in FIG.29. Auxiliary active electrodes 458, 459 are positioned at the distaltip 70 of the probe. Auxiliary active electrodes 458, 459 may be thesame size as ablation active electrodes 58, or larger as shown in FIG.29. One operating arrangement is to connect auxiliary active electrodes458, 459 to two poles of a high frequency power supply to form a bipolarcircuit allowing current to flow between the terminals of auxiliaryactive electrodes 458, 459 as shown by current flux lines 460. Auxiliaryactive electrodes 458, 459 are electrically isolated from ablationelectrodes 58. By proper selection of the inter-electrode spacing, W₂,and electrode width, W₃, and the frequency of the applied voltage, thecurrent flux lines 460 can be caused to flow below the target layer asdescribed above.

[0161] The voltage will preferably be sufficient to establish highelectric field intensities between the active electrode array 436 andthe target tissue 440 to thereby induce molecular breakdown ordisintegration of several cell layers of the target tissue. As describedabove, a sufficient voltage will be applied to develop a thin layer ofvapor within the electrically conductive fluid and to ionize thevaporized layer or region between the active electrode(s) and the targettissue. Energy in the form of charged particles are discharged from thevapor layer to ablate the target tissue, thereby minimizing necrosis ofsurrounding tissue and underlying cell layers.

[0162] With reference to FIG. 30, there is shown in perspective view anelectrosurgical probe 700, according to another embodiment of theinvention. Probe 700 includes a shaft 702 having a shaft distal endportion 702 a and a shaft proximal end portion 702 b. Shaft 702 isaffixed at its proximal end 702 b to a handle 704. Shaft 702 typicallycomprises an electrically conductive material, usually a metal, such astungsten, stainless steel, platinum or its alloys, titanium or itsalloys, molybdenum or its alloys, nickel or its alloys. An electricallyinsulating electrode support 710 is disposed at shaft distal end 702 a.An active electrode 712 is disposed on electrode support 710. Activeelectrode 712 comprises a blade electrode (e.g., FIGS. 31A, 31B). Anelectrically insulating sleeve 716 covers a portion of shaft 702, andterminates at sleeve distal end 716 a to define an exposed portion ofshaft 702 extending between electrode support proximal end 710 b andsleeve distal end 716 a. This exposed portion of shaft 702 defines areturn electrode 718 on shaft distal end portion 702 a. (In analternative embodiment, the return electrode may take the form of anannular band of an electrically conductive material, e.g., a platinumalloy, disposed on the exterior of the shaft distal end.) A cavitywithin handle 704 accommodates a connection block 706 which is connectedto active electrode 712 and return electrode 718 via electrode leads(not shown). Connection block 706 provides a convenient mechanism forcoupling active electrode 712 and return electrode 718 to opposite polesof a power supply (e.g., power supply 28, FIG. 1).

[0163]FIG. 31A is a perspective view of an active electrode 712 of probe700, according to one embodiment of the invention. Active electrode 712is in the form of a single blade electrode which extends from electrodesupport 710 to a distance, H_(b). The distance H_(b) may vary, forexample, according to the intended applications of probe 700, and thevalue of H_(b) is at least to some extent a matter of design choice.Typically, for a broad array of electrosurgical procedures, the distanceH_(b) is in the range of from about 0.02 mm to about 5 mm. Activeelectrode 712 includes an active edge 713 which is adapted forgenerating high current densities thereat upon application of a highfrequency voltage from the power supply between active electrode 712 andreturn electrode 718. In this way, active edge 713 can efficientlyeffect localized ablation of tissues via molecular dissociation oftissue components which contact, or are in close proximity to, activeedge 713. A process for ablation of tissues via molecular dissociationof tissue components has been described hereinabove.

[0164] As best seen in FIG. 31B, the blade-like active electrode 712further includes first and second blade sides, 714 a, 714 b,respectively. First and second blade sides 714 a, 714 b are separated bya maximum distance, W_(b). The distance W_(b) is typically in the rangeof from about 0.1 mm to about 2.5 mm. In the embodiment of FIG. 31B,first and second blade sides 714 a, 714 b are substantially parallel toeach other. Each of first and second blade sides 714 a, 714 b areadapted for engaging tissue severed, ablated, or otherwise modified byactive edge 713, and for coagulating tissue engaged by first blade side714 a and/or second blade side 714 b. In this way, active electrode 712can precisely and effectively sever, ablate, or otherwise modify atarget tissue with active edge 713 to form a first-modified tissue, andat the same time, or shortly thereafter, further modify thefirst-modified tissue by means of first and second blade sides 714 a,714 b. For example, active edge 713 can make an incision in a targettissue via localized molecular dissociation of target tissue components,while first and second blade sides 714 a, 714 b can effect hemostasis inthe severed tissue.

[0165]FIGS. 32A, 32B, and 32C are a side view, a plan view, and an endview, respectively, of electrosurgical probe 700 having a blade-likeactive electrode 712, according to one embodiment of the invention. Inthe embodiment of FIGS. 32A-C, electrode support 710 is disposed at theterminus of shaft 702, and active electrode 712 is affixed to supportdistal end 710 a (e.g., FIG. 33A). However, other arrangements forelectrode support 710 and active electrode 712 are within the scope ofthe invention (e.g., FIGS. 34A-C, 35A-C). Active electrode 712 is in theform of a substantially flat metal blade. Active electrode 712 is shownas being substantially rectangular as seen from the side (FIG. 32A).However, various other shapes for active electrode 712 are within thescope of the invention (e.g., FIGS. 33C-E). FIG. 32C is an end view ofprobe 700 as seen along the lines 32C-32C of FIG. 32B, showing alaterally compressed region 703 of shaft 702. Laterally compressedregion 703 may be adapted for housing electrode support 710. Laterallycompressed region 703 may also facilitate manipulation of shaft distalend portion 702 a of probe 700 during various surgical procedures,particularly in situations where accessibility of a target tissue isrestricted.

[0166]FIGS. 33A and 33B are a side view and a plan view, respectively,of the distal end of probe 700, showing details of shaft distal endportion 702 a and terminally disposed blade active electrode 712,according to one embodiment of the invention. Blade electrode 712 issubstantially rectangular in shape as seen from the side (FIG. 33A). Thedistal end of shaft 702 includes laterally compressed region 703. Asseen from the side (FIG. 33A), laterally compressed region 703 appearswider than more proximal portions of shaft 702. FIG. 33B is a plan viewof probe 700 as seen along the lines 33B-33B of FIG. 33A, in whichlaterally compressed region 703 appears narrower than more proximalportions of shaft 702. Electrode support 710 is mounted to the distalend of laterally compressed region 703. Typically, electrode support 710comprises a durable, electrically insulating, refractory material havinga certain amount of flexibility. For example, electrode support 710 maycomprise a material such as a silicone rubber, a polyimide, afluoropolymer, a ceramic, or a glass.

[0167] FIGS. 33C-33E each show a side view of the distal end of probe700 having a terminal blade active electrode 712, according to threedifferent embodiments of the invention. Electrode support 710 is mountedterminally on shaft 702, and includes a support distal end 710 a and asupport proximal end 710 b. In the embodiment of FIG. 33C, active edge713 of active electrode 712 is arcuate, convex, or substantiallysemi-circular in shape. In the embodiment of FIG. 33D, active electrode712 has a pointed active edge 713, while in the embodiment of FIG. 33E,the active edge 713 of active electrode 712 is serrated.

[0168]FIG. 34A shows in side view an electrosurgical probe 700 havingelectrode support 710 mounted terminally on shaft 702 and blade activeelectrode 712 disposed laterally on electrode support 710, according toanother embodiment of the invention. FIG. 34B is a plan view of probe700 taken along the lines 34B-34B of FIG. 34A. FIG. 34C is an end viewtaken along the lines 34C-34C of FIG. 34A. In the embodiments of FIGS.34A-C, electrode 712 is in the form a substantially flat, metal bladehaving first and second blade sides 714 a, 714 b, substantially parallelto each other. First and second blade sides 714 a, 714 b are adapted forengaging and coagulating severed or modified tissue, as describedhereinabove.

[0169]FIG. 35A shows in side view an electrosurgical probe 700 havingelectrode support 710 mounted laterally on the distal end of shaft 702,according to another embodiment of the invention. Blade active electrode712 is mounted laterally on electrode support 710. FIG. 35B is a planview of probe 700 taken along the lines 35B-35B of FIG. 35A. FIG. 35C isan end view taken along the lines 35C-35C of FIG. 35A. Active electrode712 is in the form a substantially flat, metal blade having first andsecond blade sides 714 a, 714 b, substantially parallel to each other.Electrode support 710 is mounted laterally on laterally compressedregion 703 of shaft 702.

[0170]FIG. 36A shows a side view of the distal end of an electrosurgicalprobe 700, wherein shaft 702 includes a beveled end 728 to whichelectrode support 710 is mounted. Blade active electrode 712 is disposedon electrode support 710. The arrangement of electrode support 710 andelectrode 712 on beveled end 728 may facilitate access of shaft distalend portion 702 a in general, and of electrode 712 in particular, to atarget tissue during various surgical procedures, particularly insituations where accessibility is restricted. FIG. 36B shows a side viewof the distal end of an electrosurgical probe 700, according to anotherembodiment of the invention. Shaft 702 includes a curved distal end 702a′. Electrode support 710 is mounted on distal end 702 a′, and bladeactive electrode 712 is affixed to electrode support 710. Curved distalend 702 a′ facilitates access of electrode 712 to a target tissue duringvarious surgical procedures.

[0171] Although in the embodiments of FIGS. 34A-C, 35A-C, and 36A-Bactive electrode 712 is shown as being substantially rectangular, thisrepresentation should not be construed as limiting these embodiments toa rectangular active electrode 712. Indeed, each of the embodiments ofFIGS. 34A-C, 35A-C, and 36A-B may have an active electrode 712 in abroad range of shapes, including those represented in FIGS. 33C-E.

[0172]FIG. 37A shows in side view an electrosurgical probe 700 having anexterior tube 724 arranged on shaft 702 and coupled at its proximal endto a connection tube 720 at handle 704. Exterior tube 724 may comprise aplastic tube of suitable length commensurate with the size of probe 700.Exterior tube 724 defines a lumen 726, and typically terminates at shaftdistal end 702 a at a location somewhat proximal to electrode support710. In some embodiments, probe 700 may include two or more exteriortubes 724, each exterior tube 724 having lumen 726. Each lumen 726 mayserve as a conduit for an aspiration stream, or as a conduit fordelivery of an electrically conductive fluid to the shaft distal end,generally as described hereinabove. FIG. 37B is an end view of probe 700taken along the lines 37B-37B of FIG. 37A, showing exterior tube 724 andlumen 726 in relation to shaft 702. The diameter of exterior tube 724is, at least to some extent, a matter of design choice. Exterior tube724 may comprise a substantially rigid or somewhat flexible plastic tubecomprising polyethylene, a polyimide, a fluoropolymer, and the like.

[0173]FIG. 38A shows, in side view, an electrosurgical probe 700 havingan outer sheath 722 surrounding the exterior of a portion of shaft 702,according to another embodiment of the invention. Outer sheath 722 iscoupled at its proximal end to a connection tube 720 at handle 704.Outer sheath 722 may comprise a plastic tube of suitable length andhaving a diameter larger than that of shaft 702. Together with theexterior of shaft 702, outer sheath 722 defines a lumen 726′ in the formof an annular void. Typically, outer sheath 722 terminates at shaftdistal end 702 a at a location proximal to electrode support 710. Lumen726′ typically serves as a conduit for delivery of an electricallyconductive fluid to the shaft distal end. FIG. 38B is an end view ofprobe 700 taken along the lines 38B-38B of FIG. 38A, showing outersheath 722 and lumen 726′ in relation to shaft 702. The diameter ofouter sheath 722 is, at least to some extent, a matter of design choice.Outer sheath 722 may comprise a substantially rigid or somewhat flexibleplastic tube comprising polyethylene, a polyimide, and the like.

[0174]FIG. 39A schematically represents an electrosurgical probe 700,according to another embodiment of the invention. Probe 700 includesshaft 702 and handle 704 affixed at shaft proximal end 702 b. A firstelectrode support 711 a and a second electrode support 711 b aredisposed at shaft proximal end 702 a. A blade active electrode 712 isarranged on first and second electrode supports, 711 a, 711 b. Each offirst and second electrode supports 711 a, 711 b may comprise arefractory and electrically insulating material, such as a siliconerubber or the like, as described hereinabove. A return electrode 718 islocated at shaft distal end 702 proximal to first and second electrodesupports 711 a, 711 b. Return electrode 718 may comprise an exposedportion of shaft distal end 702 a (e.g., FIGS. 32A-C). Blade activeelectrode 712 typically extends distally from electrode support 710 by adistance in the range of from about 0.1 mm to about 10 mm, an moretypically from about 2 mm to 10 mm.

[0175] Blade active electrode 712 and return electrode 718 may beindependently coupled to opposite poles of a high frequency power supplyvia electrode leads (not shown) and a connection block (e.g., FIG. 30).In one embodiment, an active electrode lead is coupled to one of firstand second electrode arms 715 a, 715 b, and the other arm terminates ina free, electrically isolated end, for example, within first electrodesupport 711 a or second electrode support 711 b. Blade active electrode712 includes a crosspiece 715 c (FIGS. 39B-D) located distal toaspiration port 734. A fluid delivery element or unit including an outersheath 722′ (e.g., FIG. 39B) is omitted from FIG. 39A for the sake ofclarity.

[0176]FIG. 39B is a partial sectional view of probe 700 of FIG. 39A asseen from the side. Outer sheath 722′ defines an annular fluid deliverylumen 726′ between sheath 722′ and shaft 702. Lumen 726′ terminates inan annular fluid delivery port 725 at shaft distal end 702 a. Fluiddelivery lumen 726′ is in communication proximally with a fluid deliverytube 721. Solid arrows indicate the direction of flow of an electricallyconductive fluid (e.g., isotonic saline) within fluid delivery lumen726′. Aspiration port 734 is in communication proximally with anaspiration lumen 732 and an aspiration tube 730. Solid arrows withinaspiration lumen 732 indicate the direction of flow of an aspirationstream, which flows from aspiration port 734 towards a source of vacuum(not shown), the latter coupled to aspiration tube 730. FIG. 39C is anend view of probe 700 taken along the lines 39C-39C of FIG. 39B. Activeelectrode 712 includes crosspiece 715 c extending between first andsecond electrode arms 715 a, 715 b, respectively (FIG. 39D). Activeelectrode 712 further includes first and second blade sides 714 a, 714b. In some embodiments, first and second blade sides 714 a, 714 b areadapted for engaging tissue that has been severed, and for coagulatingthe severed tissue. Crosspiece 715 c at least partially spans aspirationport 734. Typically, active electrode 712 comprises a single metalblade, comprising a material such as platinum, tungsten, palladium,iridium, or titanium, or their alloys.

[0177]FIG. 39D shows detail of the distal portion of probe 700 of FIGS.39A-C including blade active electrode 712. As shown, first and secondelectrode arms 715 a, 715 b are disposed on first and second electrodesupports 711 a, 711 b, respectively. In an alternative embodiment, firstand second electrode arms 715 a, 715 b may be disposed on a singleannular electrode support having a substantially central void definingaspiration port 734. In one embodiment, active electrode 712 includesboth a distal active edge 713 a, and a proximal active edge 713 b.Distal active edge 713 a, in particular, is adapted for aggressivelyablating tissue via molecular dissociation of tissue components and forsevering tissue targeted for resection, transection, dissection, orother treatment.

[0178]FIG. 40A is a partial sectional view of an electrosurgical probe700 according to another embodiment of the invention. Probe 700 of FIG.40A generally includes shaft 702 and handle 704, together with a fluiddelivery element, and an aspiration unit, essentially as for theembodiment described with reference to FIGS. 39A-D. In the interests ofbrevity these elements and features will not described in detail withreference to FIGS. 40A-C. The embodiment of FIG. 40A differs from otherembodiments described herein in having an active electrode in the formof a plasma hook 712′. Hook 712′ is in some respects analogous to plasmablade electrodes described hereinabove. For example, in one respect hook712′ is analogous to a truncated version of electrode 712 of theembodiment of FIGS. 39A-D in which one of arms 715 a or 715 b is omittedleaving one electrode arm affixed to crosspiece 715 c. From a functionalstandpoint, hook 712′ allows the operator (surgeon) to ablate tissue bydrawing the instrument towards himself/herself. In this manner, greatercontrol is exerted over the amount or extent of tissue removed orsevered by probe 700. Hook 712′ includes a first axial portion 712′ a(FIG. 40C) in contact at its proximal end with electrode support 710.Hook 712′ may further include a second portion 712′b extending from thedistal portion of first axial portion 712′a. In some embodiments, secondportion 712′b is arranged substantially orthogonal to first axialportion 712′a. In one embodiment, second portion 712′b may bestructurally similar or analogous to crosspiece 715 c of the embodimentof FIGS. 39A-D. Second portion 712′b at least partially spans aspirationport 734 (FIG. 40B). Electrode support 710 may comprise a refractory andelectrically insulating material, such as a silicone rubber or the like,as described hereinabove.

[0179]FIG. 40B shows an end view of probe 700 taken along the lines40B-40B of FIG. 40A. Hook 712′includes first and second blade sides 714a, 714 b. Second portion 712′b extends at least partially acrossaspiration port 734. FIG. 40C shows detail of the distal end portion ofprobe 700 of FIGS. 40A, 40B, including hook 712′. Hook 712′ includes adistal active edge 713 a, a proximal active edge 713 b, and an activetip 713 c. Return electrode 718 is located proximal to electrode support710. Upon application of a high frequency voltage between hook 712′ andreturn electrode 718, a high current density may be generated at each ofdistal active edge 713 a, proximal active edge 713 b, and active tip 713c. Each of distal active edge 713 a, proximal active edge 713 b, andactive tip 713 c may be adapted for severing tissue via electrosurgicalmolecular dissociation of tissue components.

[0180]FIGS. 41A, 41B, and 41C each show detail of the distal end portionof an electrosurgical probe including a hook electrode 712′, accordingto three different embodiments of the invention. In the embodiment ofFIG. 41A, hook 712′ is curved, having a convex distal edge 713 a, and aconcave proximal edge 713 b. In the embodiment of FIG. 41B, proximaledge 713 b includes serrations thereon. In an alternative embodiment(not shown), distal edge 713 a, and/or active tip 713 c may be similarlyserrated. In the embodiment of FIG. 41C, hook 712′ is curved, having aconcave distal edge 713 a, and a convex proximal edge 713 b. Accordingto various embodiments of probe 700, second portion 712′b may have alength which is less than, equal to, or greater than the diameter ofshaft 702. In the latter case, second portion 712′b extends laterallybeyond the exterior surface of shaft 702 (e.g., FIG. 41C). In each ofthe embodiments of FIGS. 41A-C, hook 712′ typically comprises a singleblade having first and second blade sides 714 a, 714 b (e.g., FIG. 40B).Hook 712′ typically comprises a metal such as platinum, tungsten,palladium, iridium, or titanium, or their alloys.

[0181] FIGS. 42A-B schematically represent a process during treatment ofa patient with electrosurgical probe 700. Blade active electrode 712 isaffixed to support 710 on shaft 702. Blade active electrode 712 includesactive edge 713 and first and second blade sides, 714 a, 714 b (e.g.,FIGS. 31A-B). Referring to FIG. 42A, active edge 713 forms an incision,I, in a target tissue, T, via localized molecular dissociation of tissuecomponents upon application of a high frequency voltage between activeelectrode 712 and return electrode 718. (The localized moleculardissociation may be facilitated by the delivery of a suitable quantityof an electrically conductive fluid (e.g. isotonic saline) to form acurrent flow path between active electrode 712 and return electrode718.) With reference to FIG. 42B, as the incision I is deepened withintissue T, first and second blade sides, 714 a, 714 b engage severedtissue in regions indicated by the arrows labeled E. In this way, thesevered tissue is coagulated by first and second blade sides, 714 a, 714b, thereby effecting hemostasis at the point of incision of the tissue.

[0182]FIG. 43A schematically represents a number of steps involved in amethod of treating a patient with an electrosurgical probe, wherein step1000 involves positioning the distal end of the probe adjacent to targettissue such that an active electrode of the probe is in contact with orin close proximity to the target tissue. In one embodiment, the activeelectrode is spaced a short distance from the target tissue, asdescribed hereinabove. Typically, step 1000 involves positioning theprobe such that an active edge of the active electrode makes contactwith, or is in close proximity to, the target tissue. Step 1002 involvesdelivering an electrically conductive fluid to the distal end of theprobe in the vicinity of the active electrode and the return electrode,such that the electrically conductive fluid forms a current flow pathbetween the active electrode and the return electrode. The electricallyconductive fluid may be delivered via an exterior tube disposed on theoutside of the shaft (e.g., FIGS. 37A, 37B), or an outer sheath externalto the shaft and forming an annular fluid delivery lumen (e.g., FIGS.38A, 38B). The electrically conductive fluid may be a liquid, a gel, ora gas. Apart from providing an efficient current flow path between theactive and return electrodes, a clear, colorless electrically conductiveliquid, such as isotonic saline, exhibits the added advantage ofincreasing the visibility of the surgeon at the target site. However, insituations where there is an abundance of electrically conductive bodyfluids (e.g., blood, synovial fluid) already present at the target site,step 1002 may optionally be omitted.

[0183] Step 1004 involves applying a high frequency voltage between theactive electrode and the return electrode sufficient to ablate orotherwise modify the target tissue via localized molecular dissociationof target tissue components. By delivering an appropriate high frequencyvoltage to a suitably configured probe, the target tissue can beincised, dissected, transected, contracted, or otherwise modified. Inaddition, the modified tissue can also be coagulated (e.g., FIG. 42B).The frequency of the applied voltage will generally be within the rangescited hereinabove. For example, the frequency will typically range fromabout 5 kHz to 20 MHz, usually from about 30 kHz to 2.5 MHz, and oftenbetween about 100 kHz and 200 kHz. The root mean square (RMS) voltagethat is applied in step 1004 is generally in the range of from about 5volts to 1000 volts RMS, more typically being in the range of from about10 volts to 500 volts RMS. The actual voltage applied may depend on anumber of factors, including the size of the active electrode, theoperating frequency, and the particular procedure or desired type ofmodification of the tissue (incision, contraction, etc.), as describedhereinabove.

[0184] Step 1006 involves manipulating the probe with respect to thetissue at the target site. For example, the probe may be manipulatedsuch that an active edge of a blade or hook electrode reciprocates withrespect to the target tissue, such that the target tissue is severed,incised, or transected at the point of movement of the active edge by aprocess involving molecular dissociation of tissue components. Inembodiments where the active electrode is in the form of a hook, step1006 may involve engaging the hook against the target tissue and drawingthe hook towards the operator in order to cut or sever the tissue. Inthis manner, the extent of cutting or severing can be preciselycontrolled. In one embodiment, step 1006 involves reciprocating anactive edge in a direction parallel to a surface of the target tissue.Typically, step 1006 is performed concurrently with step 1004. Step 1002may be performed at any stage during the procedure, and the rate ofdelivery of the electrically conductive fluid may be regulated by asuitable mechanism, such as a valve.

[0185] Step 1008 involves modifying the target tissue as a result of thehigh frequency voltage applied in step 1004. The target tissue may bemodified in a variety of different ways, as referred to hereinabove. Thetype of tissue modification achieved depends, inter alia, on the voltageparameters of step 1004; the shape, size, and composition of the activeelectrode; and the manner in which the probe is manipulated by thesurgeon in step 1006. At relatively high voltage levels, tissuecomponents typically undergo localized molecular dissociation, wherebythe target tissue can be dissected, incised, transected, etc. At a lowervoltage, or at a lower current density on the active electrode surface,the target tissue can be contracted (e.g., by shrinkage of collagenfibers in the tissue), or a blood vessel can be coagulated. For example,in step 1010 the first and second blade sides of the active electrodemay be engaged against a region of the target tissue which has beenmodified as a result of localized molecular dissociation of tissuecomponents in step 1008. The first and second blade sides aresubstantially flat metal plates having lower current densities than theactive edge. In this manner, the lower current densities of the firstand second blade sides cause further modification (e.g., coagulation) ofthe previously modified (e.g., severed) target tissue (step 1012).

[0186]FIG. 43B schematically represents a number of steps involved in amethod of severing tissue with an electrosurgical probe via a processinvolving molecular dissociation of tissue components, and ofcoagulating the severed tissue with the same electrosurgical probeduring a single procedure, according to one embodiment of the invention.The electrosurgical probe typically comprises an active electrode in theform of a single, substantially flat metal hook or blade having at leastone active edge adapted for electrosurgically severing the tissue, andfirst and second blade sides adapted for effecting hemostasis of thesevered tissue. Steps 1000′ through 1006′ are substantially the same oranalogous to steps 1000 through 1006, as described hereinabove withreference to FIG. 43A. Step 1008′ involves severing the target tissuevia localized molecular dissociation of tissue components due to highcurrent densities generated at the position of an active edge uponexecution of step 1004′. Step 1010′ involves engaging the first andsecond blade sides against the tissue severed in step 1008′, wherebyblood/blood vessels in the severed tissue are coagulated as a result ofthe relatively low current densities on the first and second blade sides(step 1012′).

[0187]FIG. 44 schematically represents a number of steps involved in amethod of dissecting a tissue or organ of a patient with anelectrosurgical probe having a hook or blade active electrode, accordingto one embodiment of the invention, wherein step 1100 involves accessingan organ or tissue. Typically, accessing an organ or tissue in step 1100involves incising an overlying tissue which conceals the organ or tissueto be dissected. As an example, in an open chest procedure involving amedian sternotomy, the thoracic cavity is accessed by making alongitudinal incision though the sternum. Incising an overlying tissuein step 1100 may be performed generally according to the methodsdescribed with reference to FIG. 43A or 43B. Step 1102 involvespositioning the distal end of the electrosurgical probe, and inparticular an active edge of the hook or blade active electrode, in atleast close proximity to connective tissue adjacent to the tissue ororgan to be dissected. As an example, the connective tissue may be softtissue, such as adipose tissue, or relatively hard tissue such ascartilage or bone. Optional step 1104 involves delivering anelectrically conductive fluid to the distal end of the probe such thatthe electrically conductive fluid forms a current flow path between theactive electrode and the return electrode, generally as described forstep 1002, supra. Step 1106 involves applying a high frequency voltagebetween the active electrode and the return electrode, generally asdescribed for step 1004, supra.

[0188] Depending on the type of procedure, e.g., the nature of thetissue or organ to be dissected, optional step 1108 may be performed, inwhich the probe is manipulated such that an active edge of the activeelectrode is moved with respect to the connective tissue adjacent to thetissue or organ to be dissected. Where the active electrode comprises ahook, the hook may be engaged against the connective tissue and drawntowards the operator of the probe to precisely control the degree ofcutting or tissue removal. Step 1110 involves electrosurgicallyablating, via molecular dissociation of connective tissue components, atleast a portion of the connective tissue adjacent to the tissue or organto be dissected. As an example, connective tissue adjacent to theinternal mammary artery may be dissected by a process involvingmolecular dissociation of connective tissue components, in either anopen-chest or a minimally invasive procedure, such that the IMA issubstantially free from connective tissue over a portion of its length.

[0189] It is to be understood that the electrosurgical apparatus of theinvention, e.g., probe 700, is by no means limited to those methodsdescribed with reference to FIGS. 42A-44. Thus, as stated hereinabove,embodiments of an electrosurgical probe having an active electrode inthe form of a blade or hook are applicable to a broad range of surgicalprocedures, such as ablation, incision, contraction, coagulation, orother modification of: connective tissue, including adipose tissue,cartilage, and bone; dermal tissue; vascular tissues and organs,including arteries and veins; and tissues of the shoulder, knee, andother joints. Thus, while the exemplary embodiments of the presentinvention have been described in detail, by way of example and forclarity of understanding, a variety of changes, adaptations, andmodifications will be apparent to those of skill in the art. Therefore,the scope of the present invention is limited solely by the appendedclaims.

What is claimed is:
 1. An electrosurgical probe, comprising: a shafthaving a shaft distal end portion and a shaft proximal end portion; atleast one electrode support affixed to the shaft distal end portion; anda blade electrode affixed to the at least one electrode support, whereinthe blade electrode comprises a metal blade having at least one activeedge, a first blade side and a second blade side, wherein the at leastone active edge of the blade electrode is adapted for severing tissuevia molecular dissociation of tissue components, and at least one of thefirst blade side and the second blade side is adapted for engaging andcoagulating severed tissue.
 2. The probe of claim 1, further comprisinga return electrode arranged on the shaft distal end portion proximal tothe at least one electrode support.
 3. The electrosurgical probe ofclaim 1, wherein the blade electrode comprises a hook.
 4. Theelectrosurgical probe of claim 3, wherein the hook comprises a firstaxial portion and a second portion substantially orthogonal to the firstaxial portion.
 5. The electrosurgical probe of claim 3, wherein the hookis curved.
 6. The electrosurgical probe of claim 3, wherein the hook hasat least one serrated edge.
 7. The electrosurgical probe of claim 3,wherein the hook comprises a substantially flat metal blade having adistal active edge and a proximal active edge.
 8. The electrosurgicalprobe of claim 3, wherein the hook comprises a first axial portion and asecond portion, the second portion being curved and having a concavedistal active edge.
 9. The electrosurgical probe of claim 1, wherein theblade electrode comprises a first electrode arm, a second electrode arm,and a crosspiece.
 10. The electrosurgical probe of claim 9, wherein theat least one electrode support comprises a first electrode support and asecond electrode support, and wherein the first electrode arm and thesecond electrode arm are affixed to the first electrode support and thesecond electrode support, respectively.
 11. The electrosurgical probe ofclaim 9, wherein the crosspiece comprises a substantially flat metalblade having a distal active edge and a proximal active edge.
 12. Theprobe of claim 1, wherein the crosspiece is substantially orthogonal tothe first electrode arm and to the second electrode arm.
 13. The probeof claim 1, wherein the first blade side and the second blade side aresubstantially parallel to each other.
 14. The probe of claim 1, whereinthe blade electrode has a maximum width between the first blade side andthe second blade side ranging from about 0.1 mm to about 2 mm.
 15. Theprobe of claim 1, further comprising a handle affixed to the shaftproximal end portion, the handle accommodating a connection block, theblade electrode coupled to the connection block via at least oneelectrode connector, wherein the connection block is adapted forcoupling the blade electrode to a high frequency power supply.
 16. Theprobe of claim 1, further comprising an insulating sleeve partiallyencasing the shaft, the insulating sleeve terminating in a sleeve distalend at a location proximal to the electrode support and defining anexposed portion of the shaft, and the exposed portion comprising areturn electrode.
 17. The probe of claim 1, further comprising anaspiration element including an aspiration lumen in communication with adistal aspiration port.
 18. The probe of claim 17, wherein the bladeelectrode includes a crosspiece, the aspiration port is located proximalto the crosspiece, and the crosspiece spans the aspiration port.
 19. Theprobe of claim 17, wherein the blade electrode extends distally from theelectrode support by a distance in the range of from about 0.1 mm toabout 10 mm.
 20. The probe of claim 1, further comprising a fluiddelivery unit.
 21. The probe of claim 20, wherein the fluid deliveryunit includes an outer sheath situated external to the shaft anddefining an annular fluid delivery lumen between the outer sheath andthe shaft, the annular fluid delivery lumen terminating in an annularfluid delivery port located at the shaft distal end portion proximal tothe at least one electrode support.
 22. The probe of claim 1, whereinthe at least one electrode support is disposed at the distal terminus ofthe shaft, and the blade electrode is affixed to the distal end of theat least one electrode support.
 23. The probe of claim 1, wherein theblade electrode is arranged laterally on the at least one electrodesupport.
 24. The probe of claim 1, wherein the shaft distal end portionis curved.
 25. The probe of claim 1, wherein the shaft distal endportion terminates in a beveled edge and the at least one electrodesupport is disposed on the beveled edge.
 26. The probe of claim 1,wherein the shaft distal end portion includes a laterally compressedregion adapted for accommodating the at least one electrode support. 27.The probe of claim 1, wherein the at least one electrode supportcomprises a silicone rubber.
 28. The probe of claim 1, wherein the bladeelectrode comprises a material selected from the group consisting ofplatinum, tungsten, palladium, iridium, and titanium.
 29. Anelectrosurgical probe, comprising: a shaft having a shaft distal endportion and a shaft proximal end portion; an electrode support affixedto the shaft distal end portion; and a blade electrode affixed to theelectrode support, wherein the blade electrode comprises a hook havingat least one active edge, a first blade side and a second blade side,wherein the at least one active edge is adapted for severing tissue viamolecular dissociation of tissue components.
 30. The electrosurgicalprobe of claim 29, wherein the hook comprises a substantially flat metalblade having a first axial portion and a second portion extending in adirection substantially orthogonal to the first axial portion.
 31. Theelectrosurgical probe of claim 29, wherein the hook is curved.
 32. Theelectrosurgical probe of claim 29, wherein the hook has at least oneserrated edge.
 33. The electrosurgical probe of claim 29, wherein thehook includes a distal active edge and a proximal active edge.
 34. Theelectrosurgical probe of claim 33, wherein the hook is curved and thedistal active edge is concave.
 35. The electrosurgical probe of claim29, wherein the hook is adapted for severing tissue by drawing the probetowards an operator of the probe.
 36. The electrosurgical probe of claim29, wherein each of the first blade side and the second blade side areadapted for engaging a severed tissue and for coagulating the severedtissue.
 37. The probe of claim 29, further comprising an insulatingsleeve covering a portion of the shaft, the insulating sleeveterminating distally in a sleeve distal end at a location proximal tothe electrode support to define an exposed portion of the shaft distalend portion, and the exposed portion defining a return electrode. 38.The probe of claim 29, further comprising an aspiration elementincluding an aspiration lumen and an aspiration port.
 39. The probe ofclaim 38, wherein the blade electrode includes a crosspiece, theaspiration port is located proximal to the crosspiece, and thecrosspiece spans the aspiration port.
 40. The probe of claim 38, whereinthe aspiration lumen in internal to the shaft.
 41. The probe of claim29, further comprising a fluid delivery unit.
 42. The probe of claim 41,wherein the fluid delivery unit includes an outer sheath situatedexternal to the shaft and forming an annular fluid delivery lumenbetween the outer sheath and the shaft, the annular fluid delivery lumenterminating in an annular fluid delivery port.
 43. The probe of claim42, wherein the fluid delivery port is located at the shaft distal endportion proximal to a return electrode.
 44. The probe of claim 29,wherein the blade electrode comprises a material selected from the groupconsisting of platinum, tungsten, palladium, iridium, and titanium. 45.A plasma blade electrosurgical probe, comprising: a shaft having a shaftdistal end portion and a shaft proximal end portion; at least oneelectrode support disposed on the shaft distal end portion; and a bladeelectrode affixed to the at least one electrode support, wherein theblade electrode comprises a metal blade having a first arm, a secondarm, and a crosspiece extending between the first arm and the secondarm, the first arm and the second arm disposed on the at least oneelectrode support, and the blade electrode adapted for severing tissuevia molecular dissociation of tissue components.
 46. The electrosurgicalprobe of claim 45, further comprising a return electrode disposed on theshaft distal end portion at a location proximal to the at least oneelectrode support.
 47. The electrosurgical probe of claim 45, whereinthe blade electrode comprises a substantially flat metal blade having atleast one active edge.
 48. The electrosurgical probe of claim 47,wherein the at least one active edge is located on the crosspiece. 49.The electrosurgical probe of claim 45, wherein the blade electrodeincludes a proximal active edge and a distal active edge.
 50. Theelectrosurgical probe of claim 45, wherein the blade electrode includesa first blade side and a second blade side, each of the first blade sideand the second blade side adapted for engaging a severed tissue and forcoagulating the severed tissue.
 51. The electrosurgical probe of claim45, wherein the at least one electrode support comprises a firstelectrode support and a second electrode support, and wherein the firstarm and the second arm are affixed to the first electrode support andthe second electrode support, respectively.
 52. The probe of claim 45,further comprising an aspiration element including an aspiration lumenand an aspiration port.
 53. The probe of claim 52, wherein thecrosspiece is distal to the aspiration port, and the crosspiece spansthe aspiration port.
 54. The probe of claim 45, further comprising afluid delivery unit, the fluid delivery unit including an outer sheathlocated external to the shaft and defining an annular fluid deliverylumen between the outer sheath and the shaft, the annular fluid deliverylumen terminating at the shaft distal end portion in an annular fluiddelivery port.
 55. An electrosurgical probe, comprising: a shaft havinga shaft distal end portion and a shaft proximal end portion, the shaftdistal end portion including a laterally compressed region; at least oneelectrode support affixed to the laterally compressed region; a bladeelectrode disposed on the at least one electrode support, the bladeelectrode adapted for modifying tissue at a target site; and aninsulating sleeve covering a portion of the shaft, the insulating sleeveterminating distally in a sleeve distal end at a position proximal tothe electrode support to define an exposed portion of the shaft distalend portion, and the exposed portion comprising a return electrode. 56.The probe of claim 55, wherein the blade electrode comprises asubstantially flat metal blade having at least one active edge adaptedfor severing tissue via localized molecular dissociation of tissuecomponents.
 57. The probe of claim 55, wherein the blade electrodecomprises a hook.
 58. The probe of claim 55, wherein the blade electrodecomprises a first arm, a second arm, and a crosspiece extending betweenthe first arm and the second arm.
 59. An electrosurgical apparatus,comprising: a shaft having a shaft distal end portion and a shaftproximal end portion; an electrode support arranged terminally on theshaft distal end portion; a blade electrode disposed on the distalterminus of the electrode support, the blade electrode including anactive edge and first and second blade sides, the active edge capable oflocalized ablation of tissue to form a first-modified tissue, the bladeelectrode adapted for engaging the first-modified tissue against atleast one of the first and second blade sides, and the first and secondblade sides capable of effecting hemostasis of the first-modifiedtissue; and a return electrode arranged on the shaft distal end portionproximal to the electrode support.
 60. The apparatus of claim 59,wherein the blade electrode consists essentially of at least oneelectrode arm in communication with a crosspiece, the at least oneelectrode arm arranged orthogonal to the crosspiece.
 61. The apparatusof claim 59, wherein the blade electrode comprises a single metal bladehaving a shape selected from the group consisting of: substantiallysemicircular, substantially rectangular, hooked, and arcuate.
 62. Theapparatus of claim 59, further comprising a high frequency power supplycoupled to the blade electrode and to the return electrode for applyinga high frequency voltage between the blade electrode and the returnelectrode.
 63. The apparatus of claim 59, wherein the blade electrode isserrated.
 64. The apparatus of claim 59, wherein the shaft comprises amaterial selected from the group consisting of tungsten, stainless steelalloys, platinum or its alloys, titanium or its alloys, molybdenum orits alloys, and nickel or its alloys; and the electrode supportcomprises a material selected from the group consisting of a polyimide,a fluoropolymer, and a silicone rubber.
 65. A plasma bladeelectrosurgical probe, comprising: a shaft having a shaft distal endportion and a shaft proximal end portion; an electrode support affixedto the shaft distal end portion; a blade electrode mounted on theelectrode support such that a substantially flat blade protrudes fromthe distal end of the electrode support, the blade electrode adapted forgenerating high electric current densities thereon and for localizedmolecular dissociation of tissue components in the vicinity of the bladeelectrode.
 66. The probe of claim 65, wherein the blade electrodeincludes at least one active edge and essentially parallel first andsecond blade sides, and wherein the blade electrode has a shape selectedfrom the group consisting of: substantially rectangular, substantiallysemicircular, hooked, and arcuate.
 67. A method of modifying a tissue ata target site of a patient's body, comprising: a) providing anelectrosurgical probe having a shaft distal end, the shaft distal endbearing an electrode support, and the electrode support having an activeelectrode affixed thereto, the active electrode consisting essentiallyof a single blade electrode, the single blade electrode including atleast one active edge and first and second blade sides, the at least oneactive edge adapted for severing tissue via molecular dissociation ofcomponents of the tissue; b) positioning the shaft distal end in thevicinity of the target site such that the single blade electrode is inat least close proximity to the tissue at the target site; and c)applying a high frequency voltage between the active electrode and areturn electrode, wherein at least a portion of the tissue at the targetsite is ablated or modified.
 68. The method of claim 67, wherein theablated or modified tissue is dissected, transected, incised, orcontracted.
 69. The method of claim 67, wherein the tissue at the targetsite is modified by electrosurgical molecular dissociation of tissuecomponents in the vicinity of the active electrode.
 70. The method ofclaim 67, further comprising manipulating the probe such that the activeelectrode moves in a direction substantially parallel to a surface ofthe tissue.
 71. The method of claim 70, wherein manipulating the probecomprises reciprocating the active electrode with respect to the tissue.72. The method of claim 67, wherein the single blade electrode comprisesa hook.
 73. The method of claim 67, wherein the single blade electrodecomprises a first arm, a second arm, and a crosspiece extending betweenthe first arm and the second arm.
 74. The method of claim 67, furthercomprising: moving the at least one active edge with respect to thetissue, wherein the tissue is severed due to localized moleculardissociation of tissue components in a region of movement of the activeedge.
 75. The method of claim 74, wherein said moving step comprisesengaging the active edge against the tissue and drawing the shaft distalend towards the operator.
 76. The method of claim 67, wherein each ofthe first and second blade sides are adapted for engaging severed tissueand for coagulating the severed tissue.
 77. The method of claim 74,further comprising engaging at least one of the first and second bladesides against the severed tissue such that hemostasis of the severedtissue is effected.
 78. The method of claim 67, further comprising:prior to said step c), delivering an electrically conductive fluid tothe shaft distal end or to the target site such that a current flow pathis formed between the active electrode and a return electrode.
 79. Themethod of claim 67, further comprising: aspirating unwanted materialsfrom the target site via an aspiration lumen.
 80. The method of claim67, wherein the high frequency voltage applied between the activeelectrode and the return electrode is in the range of from about 10 to500 volts RMS.
 81. The method of claim 67, wherein the tissue at thetarget site is exposed to a temperature in the range of from about 40°C. to 70° C.
 82. The method of claim 67, wherein the tissue comprisesconnective tissue.
 83. The method of claim 82, wherein the connectivetissue is selected from the group consisting of adipose tissue,cartilage, and bone.
 84. A method of harvesting tissue or an organ froma patient using an electrosurgical probe, comprising: accessing a tissueto be harvested; and using the electrosurgical probe, dissecting thetissue to be harvested from connective tissue, the connective tissuelocated adjacent to the tissue to be harvested, the probe including ashaft having a shaft distal end, the shaft distal end bearing anelectrically insulating electrode support, the electrode support havingan active electrode affixed thereto, the active electrode consistingessentially of a single blade electrode, and the single blade electrodeadapted, inter alia, for highly localized ablation of connective tissuevia molecular dissociation of components of the connective tissue. 85.The method of claim 84, wherein accessing the tissue to be harvestedcomprises: positioning the single blade electrode in at least closeproximity to an overlying tissue, wherein the overlying tissue concealsthe tissue to be harvested; delivering an electrically conductive fluidto the single blade electrode such that a current flow path is formedbetween the single blade electrode and a return electrode; and applyinga high frequency voltage to the single blade electrode sufficient tosever the overlying tissue via localized molecular dissociation ofcomponents of the overlying tissue.
 86. The method of claim 84, whereinthe single blade electrode includes an active edge adapted for severingtissue via localized molecular dissociation of tissue componentsjuxtaposed with the active edge of the single blade electrode.
 87. Themethod of claim 84, wherein the single blade electrode comprises a hook.88. The method of claim 84, wherein the single blade electrode furtherincludes first and second blade sides adapted for engaging andcoagulating severed tissue upon application of a high frequency voltageto the single blade electrode, and wherein accessing the tissue to beharvested includes engaging the severed tissue against at least one ofthe first and second blade sides such that hemostasis of the severedtissue is effected.
 89. The method of claim 84, wherein dissecting thetissue to be harvested comprises: positioning the single blade electrodein at least close proximity to the tissue to be harvested; delivering anelectrically conductive fluid to the single blade electrode such that acurrent flow path is formed between the single blade electrode and areturn electrode; and applying a high frequency voltage to the singleblade electrode sufficient to ablate the connective tissue adjacent tothe tissue to be harvested via molecular dissociation of connectivetissue components, wherein at least a portion of the connective tissueis removed from the tissue to be harvested.
 90. The method of claim 84,wherein the tissue to be harvested comprises at least a portion of anorgan.
 91. The method of claim 84, wherein dissecting the target tissuecomprises applying to the single blade electrode a high frequencyvoltage in the range of from about 10 volts RMS to about 500 volts RMS.92. A method of modifying a tissue at a target site of a patient,comprising: a) providing an electrosurgical probe having a shaft distalend, the shaft distal end bearing at least one electrically insulatingelectrode support, and the at least one electrode support having anactive electrode affixed thereto, the active electrode consistingessentially of a hook having at least one active edge, the at least oneactive edge adapted for severing tissue via molecular dissociation ofcomponents of the tissue; b) positioning the shaft distal end in thevicinity of the target site such that the hook is in at least closeproximity to the tissue at the target site; and c) applying a highfrequency voltage between the active electrode and a return electrode,the high frequency voltage sufficient to ablate or modify at least aportion of the tissue at the target site.
 93. The method of claim 92,wherein the hook comprises a metal blade having first and second bladesides, the first and second blade sides adapted for engaging severedtissue and for coagulating the severed tissue.
 94. The method of claim92, wherein said step c) effects localized molecular dissociation oftissue components at the target site.
 95. The method of claim 94,further comprising: d) during said step c), moving the hook with respectto the tissue at the target site, wherein the tissue is severed at thetarget site.
 96. The method of claim 95, wherein the tissue is severedduring movement of the shaft distal end portion towards an operator ofthe probe.
 97. The method of claim 95, wherein said step d) comprisesengaging the at least one active edge with the tissue at the target siteand reciprocating the at least one active edge with respect to thetissue at the target site.
 98. The method of claim 95, furthercomprising: e) during said step c), engaging severed tissue against atleast one of the first and second blade sides, and coagulating thesevered tissue thus engaged.